Will I get 30 more days from the date I extend my visa or from my original stamp expiration date?

Hi guys, quick question that I'd bet some of you know 😊. On visa exempt (30 days on arrival) and plan to extend 30 more days at immigration for 1900 (familiar with the process, done it many times here and there over the years). What I can't remember, and what my question is: Will I get 30 more days from the day I go into immigration, or 30 days from the last day on my stamp? I ask because of the upcoming holiday- I'll have to go in early because mine expires over the closed dates.... I'm just curious if I should wait till the last minute or if I could go in early next week before it gets really busy, and whether that will affect my 30 days or not 😅

Thanks for your time.