I did my Nth marriage extension at Jomtien last month and the one-month confirmation from Bangkok was due yesterday (Sunday). I've been checking the new app which I was given, but the message hasn't changed from when I first downloaded it. I figured that since I'm on one day overstay as far as my visa stamp is concerned, that I'd visit Jomtien this afternoon to check. The lady IO didn't check the tray and sharply told me that if it didn't appear on the app (which I don't have much faith in) then they hadn't received the confirmation. This will be the first of many confirmations that hasn't been on time. Grateful to know if anyone has used this app successfully recently and did the confirmation arrive by the due date?

When an application is taken "under consideration", it is pretty common for the documents not to be returned to the local office by the report back date. The addition of an app is not going to improve the efficiency of Division headquarters. Unless you have a need for urgent travel, just try to relax and wait it out.

You're not on overstay.
Your application is still under consideration until either approved or rejected.
The given date is only for when you should contact the office again.