In voyager s2e15 "Threshold" we get the information that maximum speed is warp 9.999 and if a vessel gets to warp 10 would be beyond time and space and probably exists in multiple places and points at the same time. However... in TNG "All Good Things" when Commander William Riker, admiral at the time, tries to flee with enterprise and he gives the order to go to warp 13 ...
So who is wrong? We need better script writers...
This seems more like a complaint than a question, but the "Alternate timelines" section of the Warp factor article on Memory-Alpha says it was meant to suggest the warp scale had been recalibrated (such a recalibration also happened between the original series era and the Next Generation era):
In the October 1995 issue of OMNI, science advisor Andre Bormanis stated the idea of warp factors beyond 10 in the alternative future was in a recalibration of the warp scale, as ships had gotten faster. Maybe warp 15 was set to be the transwarp threshold instead, according to Bormanis, and warp 13 in that scale would have been the equivalent of warp 9.95 of the previous scale.
According to Star Trek Encyclopedia, (3rd ed. p. 555) warp 13 from "All Good Things..." may also allude to some type of implementation of the Federation transwarp drive technology from VOY: "Threshold".
