If we take it that the Borg assign species coding, based on contact, how are the Ferengi so low in the chart?
I believe that 7of9 called them Species 180.
Were the Borg in the Alpha Quadrant really early or Ferengi manage to get lost in Delta?
The episode in which they are referred to as Species 180 is Voyager's "Infinite Regress".
The script and production notes for the episode do not offer any reason for the low number. It seems that the novels and comics are not helpful here either.
Speculating, I imagine that since the Ferengi have an indomitable entrepreneurial spirit, some could have mounted a private expedition to the Delta Quadrant and encountered the Borg there, decades prior to the TNG era and far before other Alpha Quadrant races. Naturally, they never returned to tell the tale.
Also, recall that the Ferengi were quick to take advantage of the Bajoran wormhole for trade purposes with the Gamma Quadrant. They understand that new territories mean new business opportunities.
I have little more to offer than this quote from Memory-Alpha
It is not explicitly stated how these designations were assigned, though it is generally assumed that they were simply incremental, each newly encountered species getting a number one higher than the previous. This mostly holds up when comparing numbers to probable first contact dates or vicinity to Borg space, though some anomalies exist, most notably the Alpha Quadrant species Ferengi having an unusually low number of 180 (which may suggest that at least one Ferengi ship had visited the Delta Quadrant and encountered the Borg early on in the Borg's expansion). Numbers appear to have been assigned at first contact, and don't seem to have been reused even after the whole species was assimilated.
I'm going to chalk this up to writers error. Never forget Star Trek's motto: "We hate continuity."
There is absolutely no logical flaw here any more than Leif Erickson discovering America is a logical flaw in our history. Here are possibilities: Alien zoos or abductions, video transmissions, merchant expeditions, wormholes, transwarp conduits, Borg expeditions, Feringi originally being from the Delta Quadrant, Time travel, etc. When I originally heard this on the show I just assumed, as was implied numerous times, that Feringi were a mysterious merchant race that really got around.
We don't know when in their history the Borg got transwarp but my guess is they either developed it themselves or assimilated the technology very early in their history. It's possible the Borg sent scouts to each quadrant and bumped into the Ferengi this way.
Another possibility is the caretaker who had been in the Delta Quadrant for 2000 odd years by 2371. We don't know how long he'd been looking for a compatible species to mate with. It's possible he'd been looking for a few hundred years and some Ferengi got swept up in one of his early sweeps of the galaxy.
Another alternative is the race from the Delta Quadrant who was abducting humans as slaves in the 20th century called the Brioru. Perhaps they abducted other races including the Ferengi? Maybe there is a whole planet of Ferengi in the Delta Quadrant just like there was a planet of humans.
Well, I'd like to throw in my two-cents:
In the Voyager episode, 'Dragon's Teeth', it was mentioned that the Borg came into being at least 900 years prior, but seven was unable to give details as the Borg's memory of that time was "fragmented". One could speculate, since they only advance as they assimilate, that in the early years, meeting new species would be a very slow process. Now, with that in mind, it is canon that the Ferengi bought warp technology from the Breen between 1947 and 2151 (earth time). Just because they bought it, though, doesn't mean that they knew how it worked. It's very possible that the Ferengi had a warp 'mishap' that stranded a vessel far from its starting point and that it encountered a very early Borg vessel that, itself, had just acquired Transwarp.
When you add these two events together, you get a very low designation number for the Ferengi.
The Ferengi didn't have warp drive much earlier than humans did, but the Borg were in the alpha quadrant during the middle ages. First contact between humans and the Borg happened before the Federation existed. Up until the mid 20th century, only the Vulcans, Tellarites and Romulans had warp. The Ferengi purchased it from a species that was near extinction. I suspect the Ferengi ended up in the delta quadrant due to an abduction, at which point they were discovered when the species that abducted them got assimilated. My guess is the Vadwaar, who were in the alpha quadrant during medieval times.