Common app activities list activity -- have I done it for 1 or 2 years?

if i did a project/activity from the second half of junior year to the summer before senior year, do i check off both grades 11 and 12 (seems logical to do so)?
but wouldn’t this activity only be 1 year tho? not 2? since it went from december 2020-july 2021 (close to 1 year? second-half of junior year to summer before senior)? So why would i check off both grades 11 and 12?

and i know i spent in total 40+ hours on it, 2 hours per week (not every week tho, it was like spread out over those couple months). what do i put for hours per week and weeks per year then?