When writing a simulation, it's easy to understand what capacity is. If you have four machines, you put four machines in capacity. However, it's less clear from the reference guide or the vignettes how you create a rejected seize request (in my case, this involved turning off queueing entirely). I found it eventually on the mailing list (https://groups.google.com/forum/#!topic/simmer-devel/povKK0WKyf4) but the right snippet of code or more details in the reference guide would've made it easier to understand.