If you go on the SAT dashboard, there's a small calendar on the left side of the page. If you hover over the days shaded in blue (days you studied), you can see the time you spent on SAT practice that day. I do agree it would be nice to have some sort of graph or chart that lets you see the amount of time you've spent studying in the past days/weeks/months, or even just the time you've spent studying in total on Official SAT Practice.