All the advice you have been given about getting the 30 day extension to avoid an overstay is correct.
In case you don't know the first day you arrive - even if it's after 11 pm - is day one (not day 0) so the 30 days is up on what you may otherwise count as day 29 of your holiday.
I got mine with proof of accommodation for 1 month. I had booked 1 month at a single location.
The METV Visa allows you to enter multiple times for up tp 60 days each time( with 30 day extension possible) in the 6 month period. You can't stay continuously for 6 months but by taking short border bounces at the right time stay for almost 9 months.