to measure, to calculate
蒦 centers on the act of measuring and calculating, using tools or standards to determine size, quantity, or value.
蒦 is a phono-semantic compound: the top 艹 (grass) suggests a measuring tool made from plant material, while the bottom 隻 likely contributes the sound. The exact historical development is uncertain.
The grass top 艹 suggests a ruler or measuring stick made from a plant, and the bottom 隻 looks like a hand holding a tool. Together, 蒦 is a tool for measuring and calculating.
For ワク, imagine using a wacky ruler made of grass to measure: wacky -> ワク, and the wacky tool helps you calculate.