How does the Finish No Later Than (FNLT) constraint affect my project schedule?
Project Central uses constraint type rules, along with work durations and dependencies, to determine the scheduled start and scheduled end dates of work items in your plan. With FNLT selected as the constraint type, the Scheduled End date will be the earlier of the date entered or the end based on any dependencies. The Scheduled Start date will be the later of calculated end - duration or the start based on any dependencies. This article describes how the FNLT constraint works.