Given the negative social perception of screen time, wouldn't the parents be motivated to report lower than actual numbers? Furthermore, this is one population (Singapore) and doesn't detail (at least not in the summary) how screen time varied from day to day (eg my children have substantially less screen time on school days, than weekends. Screen time in both cases tends to be biased towards breakfast time, when the house is a bit manic, or after significant periods of outdoor/energetic activity when everyone needs a rest.)