vtx changing by radiomaster tx12

hello i’m about to start learning of ardupilot, i’m trying to set vtx, i have repere exteme foxeer with max power lvl 2.5W, but max value in ardupilot is 1000, how it can be fixed, also I’m using radiomaster 12, I set min value is 25, but on osd min value is 0, and second value is 1000, when corresponding aux is switched, third pos of aux doesn’r change vtx value, could you please help me?