Calculating utilization as a percentage

I have a VR arcade with twelve stations. 

The arcade is open varying hours each day. I have this is a table with:

Day Name | Open | Close | Total Hours

Monday | 16:00 | 21:00 | 5

I have a date table that includes all dates, with Day Name that has a relationship to the hours table.

I have sessions. These can be for 1-12 stations, for a given date and time, and a number of minutes (30/60/90). Sessions have:

Date | Time | Number of Stations | Duration | Total Minutes

2019-08-26 | 18:00 | 4 | 60 | 240

The date has a relationship to the date table.

What I want to report on is utilization for my given report page, based on a slicer on the date table.

Essentially it's:

Total minutes of all sessions

-------------------------------

Total possible minutes during operating hours

I'm just too new to all this to figure out how I make this work. I can use calculated columns on each to total up the individual rows, but I don't know how to bring the two together. I even put them on a gauge, but how would I show a card with a percentage for a given time window?