The page specifies the price is hourly and doesn't seem to list that restriction. Could you please link to where it is specified?

Edit: I don't think you're right. I've checked the Scaleway console and it appears the minimum unit of billing for this is one hour. I'd check, but they're out of stock.

Second edit: I missed the part where it says 24 hour minimum period on the instance setup page:

"As required by Apple License, you must keep this instance at least 24 hours. You will be able to delete it only after 24 hours."