is the 10 concurrent call limit across the phone numbers or every phone number can have 10 concurrent calls, (say if we have 10 number thent total calls will be 100)

10 concurrent calls means - 10 simultaneous calls across 10 numbers

Vapi 10 concurrent call limit applies to the entire account, not per phone number, so even with 10 numbers, you’re still limited to 10 total concurrent calls unless you upgrade to the Enterprise plan..