the crysmiss86 theory:

the shop number ends in a 1 or a 6, the restock time is 0 and 5.

If the shop number ends in a 2 or a 7, the restock time is 1 and 6.

If the shop number ends in a 3 or a 8, the restock time is 2 and 7.

If the shop number ends in a 4 or a 9, the restock time is 3 and 8.

If the shop number ends in a 5 or a 0, the restock time is 4 and 9.

works for every shop in marada
taken from courtneyparsons1