The only way you will be able to measure it is to count the reel before you put it on the machine, count them when they come off and deduct the amount expected to be placed. you will then have the result of attrition on the machine.
Pick the parts from the drop tray/bucket and hover the inside of the machine/between feeders and count it manually.
Both not really credible methods - with this kit your using i would just get the operators to monitor the amount of parts found in the machine after each run and bag em (low value)then weigh it. That can be you KPI method!?
Even machines that count (I have 7 Europlacers and one Samsung Quad) and use the PROMON software to monitor waste and it's very good for measuring KPI's and monitoring machine faults, but even this is not absolute.
My attrition rate per machine is usually 0.78% - it makes the owners happy to see that rate! =)
We dont count parts at all.