In Terraform Cloud there is a usage page to view information about Terraform Cloud orgs. The page is shown below and is located on the left side of the window for org owners:
The number under the Concurrent run limit reached panel may exceed the number of concurrent runs in the org. It represents the number of times that runs were queued and waiting because there were already a maximum number of runs active in the org.
Hitting this maximum value is not a problem as all subsequent runs will queue and wait to execute until there is an available run slot. The purpose of this metric is that it can demonstrate how often there are runs sitting in a queued state in the org. If it happens quite often, it may be beneficial to add additional concurrent runs to the org.