Each Membership plan differs by the size that defines the number of operations available with domains at cost price. E.g. Basic S plan makes it possible to perform 100 operations with domains at Openprovider's cost price. The operations are: registration, renewal, and transfer.

For your convenience, here is the reference table with the maximum number of available operations (plan capacity) with domains included into Membership plans:

The current usage of domains in the plan is displayed in the active Membership plan details:

The counter:
In the example above the reseller has performed 1 out of 500 operations (Domains: 1/500) since 17 June 2019. This counter displays only the number of operations performed while the current Membership plan was valid. It does not reflect the total number of domains in your portfolio.

Let's say that you have 600 active domains and the counter says 1/500 since 2019-06-17. This number means that only 1 domain from your portfolio has been registered, renewed or transferred at the cost price from 17 June 2019. You still have 499 operations for costprice available.

If other domains are eligible for the operations at cost price and any operations are processed, the counter will increase with every operation.  1/500 --> 2/500 --> 3/500
When the counter reaches 500/500, the membership will auto-renew, if the balance is sufficient (in the above example the Auto-renew is ON). 

If some of the 600 domains are not eligible for the operations at cost price, they will be invoiced at the general "non-member" price that applies and the Membership counter will not increment.

You can find the prices of the extensions in your control panel.