I was in a lab group last year as an undergrad and my Prof/ Supervisor offered me to apply for NSERC with him a few times but I declined... so I’m probably not the most qualified to answer this question.

But based on our discussion, the $4500 is not given to you in whole. They divide it and you get a chunk of it per month. Then depending on how generous your supervisor is and how much funding he has, you get extra compensation on top of the $4500. My supervisor was v generous, but the minimum that they can add is around $3800.

[Edit]: I don’t think they compensate you by the hours you work. I dont know about the other labs, but most lab I know don’t really keep track of the hours. Some days you work way more, some days it’s pretty chill. Depending on what’s going on with your experiment