If we're reading it right, it's that we can't have any new players who weren't on last seasons A list unless we have a positive spend on players who were on that list.
So getting money for say, Moreno doesn't help. It also means we can't use Malen or Garcia in Europe unless we have a positive net spend as they weren't on that list last season.
But ironically we could use Disasi if we bought him, presumably.