I had noticed this also when my elderly aunt was having a 'study'. 2 or 3 people would come and stay a couple hours visiting, maybe read a few paragraphs and leave her some literature. Oh, yeah, and she would always give them some money. I suppose only one of them could count the 'study' but the others could count the time and probably a return visit. My aunt is now 90 and will never go to another KH or assembly because of her health. The only good thing is it was company for her to break up her boring day and the wits got to count all that time on one person that will never be a publisher again.
The same thing happened when my father was in the hospital just before he died. 3 ladies came to visit him. It was obvious they were in field circus. They drove about an hour each way to the hospital and stayed about 15 or 20 minutes. One lady left the WT and Awake! and told him he could give them to his nurse. I figured that was a good 6 or 7 hours of time counted plus 2 mags 'placed'. Then dad could have 'placed' the same mags again with his nurse - had they not disappeared shortly after the ladies left - oops, where did those things go?