It's really more a matter of where on the pattern (or where on the sweater) do these measurements match up. The one on the right divides the body of the sweater from the armhole opening at the point of the beginning of the armhole bind off. The one on the left divides the body of the sweater from the armhole at the end of the armhole bind off.
It looks like those are the armhole lengths. The one on the right edge is from the undearm to the shoulder shaping. The one on the left is from the last dec to the shoulder seam. And/or they may be different for the front than for the back. The written pattern will say which measurement to use when.