When setting up allocations in the Modern User Experience (UX's) Staffing module, for certain resources, if you assign an allocation of 50%, Clarity will assign 0.53 or 0.52 instead of 0.50 in some of the columns.
Release : All Supported
Component : CLARITY RESOURCE MANAGEMENT
This is by design and due to the resource's availability not matching the standard calendar. See the following KB for more details: FTE incorrect if availability does not match the Standard Calendar.
To check if this is the cause:
Note: Another thing to check if it not consistently the same amount each month is whether the user has any vacation time/holidays on their calendar that aren't on the Standard calendar.