It shouldn't be too hard to guess a reasonable approximation for the largest matrix that you can multiply in 10 minutes. You don't need to be super accurate, as long as you're in the right ballpark. I would just submit a handful of jobs with sensible intervals, and then look at where you start to exceed the time-limit. Perhaps you can repeat this twice to get a more accurate number if you feel your initial intervals were too large. Unfortunately, we are having an issue with our Setonix allocation, which is making the jobs take a long time to start (see my latest announcement on LMS). I know this is frustrating, I am doing my best to fix it ASAP.