Single post in Reminder: Do NOT Multi-post 25/11/2019

Hopefully this is the correct place to make an inquiry about art shop updates. If you're in a situation where:

• you have just completed someone's order or commission and are ready to publish it
• someone else, ie a different customer, is the last person to post as opposed to you, the shop owner
• that post does not contain an order or commission request in it

Is it acceptable to post the results then and there? On one hand, you're not multi-posting by the strictest definition of the word because you're not the last poster; on the other hand, there's nothing within the last post itself that is demanding that a new post be made to address it, so it may fall under spamming if not a variation of multi-posting in itself. Or is there a time period wherein that's acceptable within the usual two-day limit? Say, within two hours or four hours of that last post?