I do not know of a function you can call to get that number dynamically.
My question is if you actually need to do it this way. I know by experience you are used to pool instances in order to diminish memory garbage and allocation. Now all these objects are actually already pooled. (hence the max values in game.project) Using any kind of factory.create is therefor building up the objects all from pools and are impacting very little on performance and memory allocation.
Have you done a comparison on this to see if you actually need your own pool tech.
Still I can agree that it would be interesting to have access to the values (as the engine is retrieving them anyway when using the engine profiler).