New Holland 678 belt length

We have 2-678 round balers. The designated belt length is 343” with a maximum variance of 1.5”between belts. My question is this-
What is the absolute minimum length that all the belts can be?

My brother and I are now in the drivers seat so to say as our Father is no longer able to do anything due to health issues. He was definitely an Alpha male so we did just as he directed. Previously when we would relace a belt I never saw him measure belt lengths. We merely cut the ends relaced and threaded it back into the baler. I can’t say I ever saw an issue with bale quality but I don’t recall ever rolling bales when I was positive that all belts were of equal length.

New Holland 678 belt length