How are Employement Insurance benefits calculated when working multiple jobs?

Currently working two jobs, will soon get laid off my main one and continue to work my side job. In my main job I make about $900/week, and in my side one I make about 100/week. I understand that .50 off every dollar I make at my side job will be subtracted from my benefit, but my question is how will my initial benefit be calculated? Will they use 55% of my main job ($495) as the base amount, or is it something different that combines the two weekly amounts? I would really love to not be too surprised by the amount they throw at me, thanks in advance for the help!!

Edit: basically, I’m wondering if there’s any way that going into EI already working a part time job can hurt my benefits (other than the $.50/dollar earned reduction)

Well I have no idea what jurisdiction you’re talking about, but it’s probably based on the job you’re being laid off from alone.