There had already been two kings of England named Edward before, why is it they weren't taken into account? What's even more is that Henry III even named him that because he adored Edward the Confessor, so it seems even more odd.
hi! you may be interested in these posts
Why did the regnal numbers for the Kingdom of England reset after 1066 but not reset upon creation of the Kingdom of Great Britain? - /u/Algernon_Asimov and /u/Skittles_87 explain that regnal numbers were introduced in England by the Normans
Why was Edward Plantagenet dubbed "Edward I" when he was the 4th Edward to rule England? - /u/Valkine looks more closely at Edward I
more related discussion here