Checked their site, it's subject to FUP(fair usage policy), basically, it says unlimited but if you cross a certain ***GB mark, you will get slower speed, but still have access, unlike the ***GB plan where you just lose access if you consume it all.

From their FUP

If an account’s usage exceeds the limits IDM deems fair and reasonable for a residential broadband service during given periods, ..., IDM will apply daily and monthly speed limiting restrictions during these periods to the account in question

Knowing that IDM currently owns Cyberia(or is merged with them), the limit during the "unlimited time"(previously 11pm-7am) is equal to the limit you have per month (so if you had 10GBs per month, during the 11pm - 7 am time, you're allowed to use 10GB across the month before they slow your internet during that time), that's basically my experience with cyberia. So if it's unlimited but costs similar to 120GB per month, just assume that after 120 GBs you'll get the speed throttled.