@Sadri ******
I understand, this it’s no official site and there’s in fact nothing such as a 7 days extension, but they will probably give you a 7 days extension denied stamp and know what you’re looking for at the immigration.
Someone might call this an extension on a VOA as it’s not. If you try to apply for two extensions on a tourist entry you’ll also get an extension denied stamp and 7 days to leave.
I don’t have a complete overview but I’ve not seen feedback of someone denied extension denied stamp and 7 days to leave, so you’ll probably be fine.