Gitlab-Runner: Register multiple runners per machine

I am trying to figure out the best way to make use of a powerful machine I have for the purpose of CI/Testing. Currently I have a single gitlab-runner instance next to a single docker instance on the same machine. The gitlab-runner has two docker-type runners registered to it.

One is tagged with a GPU and the other is not tagged. My thoughts here are that if a task needs the GPU it can use the runner with the GPU tag, and if it doesnt need a GPU it can run on the CPU only runner.

My question is: Will the runner launch off docker containers from bother registered runners at the same time?

So far through my testing it seems to be using just one of the runners on the machine at a time, then when it is done it switches to the other runner's task.

Does Gitlab-runner only launch off one docker at a time, or does it have the ability (given you have more than one docker-type runner registered) to launch off multiple docker container CI-tests at once?