This is not an issue just geeky stuff.
Joined PP with my calculated Useage G:17250 E:2000
Just checked 10/01/18 - 12/01/19. G:16942 E:1991
Industry advises PP. G:19285 E:2410
It all comes out in the wash and in money terms the industry calculation v my joining projection is £120 more a year.
Sorry not very interesting...zzzzzzz