How do you let a user have priority over X cores

Is there a way to let a specific user have high priority in up to X cores concurrently ?

Could you please give us a more background and goal of this use case.
Short answer based on the query would be advanced reservation.

The use case:

Suppose a user buys a node, and we join that node to the HPC.

We would like to give that user a higher priority since he/she contributed a node.

One option is to give him priority to ‘his’ node. But another option, which we prefer, is to disregard the actual node, and just give that user priority over x cores in the whole pool, where x is the number of cores that his contributed node has.

Please check the PBS Professional Adminstration guide for server and queue limits.