Many people have grumbled about this.
The problem is that the message is wrong.
If you click on "Edit", shortly after posting, you will see a message above the edit box telling you how many minutes of editing time you have
left.
This message appears to count down from 120 minutes.
This counts as "4 hours" in the ATS universe, even though it's only two hours in the rest of the world.
Yup, it is generally two hours, although that's varied sometimes...
That particular part of ATS is a bit finicky in my experience, but alas there is hope on the horizon. Our owner is currently working on a redesign
and eventually the site will have a full update and most problematic issues such as these will be resolved.
In the meantime, you can send any mod a PM or file an alert with what you'd like to edit and where. Staff are always happy to assist.