Listing Enhancement Impressions

[Chelsea Malibu]

On the listing enhancements report in MP, how are these impressions calculated? Are these actual views at the time the java script allows them in their viewer or are they part of just that run of add in the java console at that time.  Only 3 show at a time and am wondering if its part of that scroll since they run many scrolls meaning and that you may be in the script but not actually seen.  So, that number could be counted and not actually seen content unless they stay on page long enough for all to scroll through. 

(and if you don't know on this, please don't chime in to just guess or tell us you don't know)