These are only fields for differentiate salary.
Example from one my project:
pay scale type :Central office, regional office, shops
pay scale area :Capital, cities, small town (You can set your own differentiation)
pay grade : 01,02,03 (junior employees,11-15 ( managers)19 (directors),20 (general director). Read about HAY grade system.
pay scale level is : .For combination of above element and grade 20 is scale 60000$ - 200000$
You can devide it on levels for your own purposes.
E.g. 60000 - 90000
80000 - 120000
100000 - 150000
130000 - 180000
160000 - 200000
It may depends on length of service or something other.
For SAP Salary there are no meaning