Sure thing. The pumps IOB calculations that I have been exposed to are a First in, first out calculator with a non-programmable decay rate. So for example if you took 5 units of insulin. Immediately after injection the IOB would show 5 units, then after a unit of time expires you would have 4.75 units onboard, and it will decay until you hit the total insulin duration time (which can be programmed in most pumps, although not in Control IQ) then it would show 0 IOB.
If you take additional insulin while there is still IOB, it would add the second insulin bolus to the IOB and start calculating that in the same way.
So cumulative record of bolus insulin. None that I am aware take other factors into accounts such as what Eric hypothesized, which would be awesome.