I prefer to use Potential Score instead of two numbers for cap range.
This value shows how many potential was used and it's easy and intuitive to see how many potential remain to train.
http://bbtools.x10.mx/potencjal/For example potential = allstar means that player should be capped when Potential Score is between 6,00 - 6,99 (depending on sublevels of potential). For other levels of potential it works analogical.