Resource availability is 100% in calendar settings, however in the capacity module using an FTE view, availability is 115%

Our global calendar settings are as follows:

Default number of hours a day = 7

Days in a month = 20

Default Members Availability(%) for New Project = 100%

On the Capacity Planning module (Demand vs Capacity view) using the FTE and Monthly views, I would expect to see an Capacity of 1 per resource based on their 100% availability. However, in some March, they have 1.15 available capacity and in April 0.95 available capacity as shown in the screenshot below. Any reason this is happening and any way to resolve this?