Offer in Compromise- once accepted is that a flat amount or does it accrue interest?

Hi! I used the Offer in Compromise Pre-Qualifier tool and it said I may be eligible to settle for an offer of:
Option 1: $2750 within 5 months or
Option 2: $2750 over a 6-24 month period.

My question is if I apply for an Offer in Compromise for this amount, and it gets accepted for over a 6-24 month period, does that mean I have 24 months to pay that full amount of $2750 flat, or does that amount accrue interest over the course of that 24 month period? Thanks so much!