The Full-Time Equivalent (FTE) seems to be incorrectly computed for resources whose availability does not match the Standard (base) Calendar
Steps to Reproduce:
Expected Result: We were expecting the resource availability will be one (1) FTE since you do not have any allocations for that resource and they are working all 7 hours as per the resource calendar.
Actual Result: The resource availability is shown as 0.88 (which is 7/8).
This is working as designed. FTE is calculated based on the Standard Calendar not a resource's base calendar. So, if the standard calendar has 8 hour shifts, and a resource's availability is 7, it will divide the 7 hours of availability by the 8 hours on the standard calendar.
Similarly, if the standard calendar has more/less workdays than the resource's calendar, the FTE will divide the resource's availability by the availability on the standard calendar for that same period. For example, if the standard calendar has 19 eight hour work days for one month and the resource has 20 eight hour work days for this same month, the FTE for the resource for this month will be 20 divided by 19 or 1.05 FTE.
This applies to both the Classic and Modern UX.
KB29080: How is full-time equivalent (FTE) allocation calculated?