There is a documented bug that has total float calculating increased total float for LoE activities. There is an enhancement request to fix it and there are also workarounds.
DESCRIPTION OF ENHANCEMENT REQUEST: Ability for Level of Effort (LOE)
activities to be excluded from the Longest Path like in P3.
Problem/Issue? LOEs and completed activities are included in the path in Project Management.
LOEs or WBS Summary activities will never be at the end of the float
path (the seed most critical activity that begins the path), but if an
activityhas predecessors or successors that are LOEs they will form part
of the path.
POTENTIAL WORKAROUNDS: 1) Calculate 1 multiple Free Float Path on Schedule
Options Advanced tab and group layout by Float Path.
2) Run filter "Where Float Path equals 1"
Activities on Float Path 1 should be the same as activities on longest path
This makes some activities (which are not LOE) show up on the longest path even though they shouldn't.