I think it's just a lot of guesswork, could even come from computer games and the like. It could be that if it's not accurate then it's equally inaccurate for all teams I suppose, and that they'd still be at the same sort of rank in terms of how much they spend compared to others but who knows? Could also just be way off in that sense too.
We won't know anything for sure about Wrexham's accounts for this season for another 11 months or so when the next set of accounts are released.
A slight clarifier too on the £11m figure from when in League Two, that was total wages, not just for players. It was all club staff so playing staff will have been lower than that. Stuff like that for lots of clubs is out there if taking a deep dive as accounts are out there, they're just ayear behind but individual players wages are never really out there without a lot of guessing going on down in these divisions. Another of these sites has them at £10.67m ($14.2m) for this season -
https://www.capology.com/club/wrexham/salaries/ and none of them can really know.
Stuff we do know from digging through some press articles following the release of official accounts, could dig out more clubs in different divisions for comparison but I can't be bothered:
Wrexham 23/24 total wages - £11m (playing and all non playing staff) League Two
Wrexham 22/23 £6.9m - National League
Bradford 23/24 £6.1m, League Two
Charlton 23/24, £12.1m League One