So how is it you lose 5 units in baseball but you gain half a percent "ROI"?
I use the term ROI interchangeably with profit margin. Some people use it as a measure of fluctuation in bankroll, but I find this to be a flawed concept because you aren't necessarily investing money that is sitting in your bankroll. I calculate ROI only on what has been wagered.
If you go 0-1 on your first day and lost 1.1 units, you have an ROI/PM of -100% and are -1.1 units
If you go 1-1 on your second day and lost 0.1 units, you have an ROI/PM of -36.4% and are -1.2 units
So your ROI/PM can go up even if you lost units overall in the same day.... just as you can gain units and lose ROI/PM in the same day.