Are challenge star pt calculations off?

Only level 31/2x round pass w/ skip had 832 got 2x star count = 36 bringing score to 918 then instead of getting 62 my score went to 930 only giving me 12 more pts? I believe it should be 980 with x2 @ 31? Am I miscalculating ? Halt game play until someone can explain have more dbl round passes don’t want lose if problem with calculating them ! Can someone explain please?