The sound of "gh" shows up as "3". Hopefully there's a way to have this corrected for post-beta phase because it would be helpful for phonetics!
It seems to be: ع showing up as "3a" when it sounds like "gha". غس shows up as "3us" when it sounds like "ghos/gos".
Thanks to everyone who put this together!!
3 is the best way to represent ع.
The apostrophe works for ء but the apostrophe can't be both ء and ع because they are different. The 3 looks the same as the ع, just backwards, and as Juliet mentioned, it serves a reminder to English speaking learners that it's not a sound present in English. Furthermore,3 is how many Arabs all over the world represent the ع when typing in Arabic to each other, and you'll be able to recognize that if you learn it as it is here.
What I don't get is why they don't extend this to 7 for the ح.