How many users can use a Silver account?

I assume that you are referring to sub users. Is that correct?

If yes, please note that this feature is available only on the JotForm Enterprise plan and not on regular paid plans.

When this feature was available on regular paid plans, you could add up to 10 sub users on the Silver plan.

Here is a related link for reference: https://www.jotform.com/enterprise/faq/