What the figures show
In this fictional four-week example, net sales excluding GST are $42,000 and guest covers are 2,100. Net sales per cover are therefore $20.00. The calculation is valid for the stated inputs, but it does not establish staffing adequacy.
What is still needed
Sales and covers by comparable trading periods, matched paid labour hours, role coverage, preparation and closing workload, and service-quality context.
The next step
Reconcile the information before comparing roster options. Assign responsibility and define the measure that would verify any later authorised change.