Question: How many days does the 3 month multi entry visa for Vietnam cover

My flight is from Melb(Aus) to SGN to HAN to Paris, being in Vietnam on the 3rd of July. My return flight is from Paris to HAN to SGN to Melb, being in Vietnam on the 3rd of Oct. Since Oct 3rd is 92 days from July 3rd, I’m wondering if the 3 month multi entry visa to Vietnam will cover my travel days, or does 92 days just fall out from the ’3 month period’?