How can I make Pierre sell only a certain quantity of seeds?

[qpqpqp121]

I want to sell only a fixed quantity of seeds in Pierre's store, like the Krobus store, but I don't know how.

(ex. Only sell 5 parsnip seeds per day)

Is there a relevant mode or source code to reference?

I am not good at English so I wrote it through Google Translate.
Meaning may not be conveyed properly.

Edited December 24, 2019 by qpqpqp121