Thanks for all of the responses.
My daughter stopped by today and I took a look at the belt. I can't get to checking the tensioner range today but will try to get to it in a week or so.
The new belt part appears to be 83 inches (830K6 and 6PK2110 on belt). I know the parts lookups I have done spec the belts at 82.68 to 82.72. Will the extra 1/4 -1/3 of an inch make a difference? I suspect it might once the belt ages and stretches but not early on. If so I might take it back in a few weeks and tell them to put on an exact match.