Help, how does a guest accept a change to their reservation

I’m new to air bnb and have my first booking, guests due to arrive on Monday. Originally he wanted to stay from Monday 25th of January and check out on Friday 29th. However his plans have changed and he needs to check out on Thursday 28th. I’ve amended the booking and from what I can see he needs to “accept” this but he can’t seem to find out where he “accepts” this change. I’ve looked through all the help pages and can’t find the correct information for him. Thank you for any help.

He should have gotten an email with the notice to change. Have him check his reservation page. He also can request the change. I had a guest who had a bit of trouble figuring it out, but she did eventually.

If they look on a computer (as opposed to the app), it should be at the top of the chat message thread. Most guests can find it but I also had one guest who was completely unable to find it. Not sure why that is