discrepancy between circle recorded app time and device screentime

many of our devices are being shut off from internet connectivity by day time limits that just do not correspond with the actual screentime at the devices themselves. For example we recorded Circle apply a cap on usage of snapchat after 90 mins, whereas the actual recorded screentime until that same point was only 18 mins. In this way the timelimits make no sense at all. 

What is the cause for the discrepancy and how can we solve this? 

tx, Ynse