The ASPT sets the total number of concurrent policies an Action Server can run. When the ASPT is reached, if there is only one Action Server and it is running the maximum number of policies, any additional policies that are started will be queued. Policies that are queued remain in the queue until a running policy completes its execution, freeing up a policy slot. After there is a free policy slot, the first policy in the queue is instantiated on the Action Server. Policies are taken from the policy queue in a first in, first out (FIFO) model.
Unfortunately, there is no easy way to see how many policies are queued or which policies are queued. Queued policies are stored in the POLICY_PUBLISH_QUEUE table in the database; to determine how many policies were queued, you can view the contents of that table. The OOC policy view totals include queued policies, but there is no way to filter on queued policies as you can with those that are running.