VPF Rules - Regulations for Employer - VPF contribution would be fix per month or it will be % based on Basic?

Hi Experts , I would require few clarifications regarding VPF , we are going to start VPF contribution in our organisation from April 2020. so required suggestions on below Points from Employer Point of view.
1- Our organisation deduct PF based on restricted basic option , means 15000x12% = 1800 pm is fixed for all. So can we start VPF in this case ?
2- VPF contribution would be fix per month or it will be % based on Basic ? if it is fix then the fix amount will deduct every month , but if it is percentage based then the amount may vary because of Leave without pay and other components.

What I practice is as follow-
suppose if Employee wants to contribute 4000 over and above 1800, than their total contribution will be Rs 4000+1800= Rs 5800/- which is the 12% of Rs 48333/-
If employees salary is up to this range (Rs 48,333) than, employee can contribute that much. In short, employee can make maximum contribution of their salary (12% of maximum salary)
While generating ECR-
Keep EPF Wages as- 48333
EPS Wages- 15000
EDLI Wages- 15000
UAN#~#Employee name#~#48333#~#15000#~#15000#~#15000#~#5800#~#1250 #~#550#~#0#~#0
A/C 2 inspection charges will be deducted on EPF wages.
We are just contributing extra employee share, employer is contributing on 15000 only.