This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 筿 is uncertain. It visually combines 竹 (bamboo) and 条 (article, line), but the original semantic or phonetic role of these components is unclear.
The top is bamboo 竹 and the bottom is a line or article 条. Picture a thin bamboo strip used for writing or weaving, but its exact meaning is uncertain.
For ショウ, imagine a bamboo shoot (ショウ) growing in a neat line: shoot -> ショウ, and the bamboo 竹 top connects to the 条 bottom.