概

Left tree radical anchors 概 in the wood family. Originally 概 named the leveling stick of wood that was scraped across the top of a grain measure to give an exact, flush amount - hence the modern meaning 'rough total, general estimate.' Same radical: 板 plank, 枝 branch, 杆 pole, 模 mold.

Right side 既 supplies the sound, jì drifting to gài through historical k/j alternation. 既 itself depicts a person turning away from a bowl of food they have already finished - 'already done.' That sense of 'finished, summed up' fits the leveling-stick metaphor of 概: once you have scraped, the count is final.