From the VM provider website, download the Closed Tickets CSV with the selections from the image below for the desired garage and month. Make sure to include 1 or more weeks past the desired end date - this is necessary for the formulas to produce a proper result for the intended last day of your selection.
Create another sheet in the resulting file. Edit the sheet to be a table of hours from 0:00 to 23:00 for the columns, and dates from the 1st to the last day of the month for the rows. Note that cell A1 should be blank.
Enter the following formula in cell B2:
=COUNTIFS(Transactions!$A:$A,"<="& ($A2+B$1+1/24),Transactions!$B:$B,">="& ($A2+B$1))
where Transactions should be changed to match the name of the first sheet (the sheet that contains the Enter and Exit times).
Apply this same formula first across the columns, and then down the rows (Excel will only allow you to apply formulae in one direction at a time).
Once the data has been generated, select the full range of data and apply Conditional Formatting -> Color Scales -> Green-Yellow-Red Color Scale to produce the occupancy heat map as shown below.
