It’s at least higher than 11. I think maybe around 14-15?

In order to unlock everything you can in the basic store (some options of which you need to upgrade in order to level up familiarity past a certain point - like to level 2 - as well as eventually unlock/be able to move into the other room) is by using hearts to clear out all boxes (even those with items sitting on top of them - like the radio). Make sure to complete the tasks listed in the white silhouette next to the familiarity meter.