Random tick / Scheduled tick

How does random tick work?

Chunks consist of one subchunk per 16 blocks of height, each one being a 16×16×16=4096 block cube. Sections are distributed vertically starting at the lowest y level. Every chunk tick, some blocks are chosen at random from each section in the chunk. The blocks at those positions are given a "random tick".

——Minecraft wiki

CustomCrops give blocks random tick every second. The default value of random-tick-speed is 20, which means the plugin would choose 20 random blocks every second from a 16x16x16 section.

This image shows how scheduled tick work