Each list can have up sixty (60) groups.
The group title is like an overall category for your groups, to keep similar options together. You can have multiple sets of groups; group titles don't count toward the 60-group limit. The options under the group titles are the actual groups that are counted. For example, you could have 3 group titles each with 20 different groups in them, 6 group titles each with 10 groups, or any other combination with up to 60 total groups.
Tip: It's best to choose something descriptive like "What are your skills?" for the group titles if you're asking subscribers to choose from the groups. For example, title one set to ask subscribers the topics they're interested in (and then add groups for the topics you'll email about), and a second set to ask how often they want to receive email (with groups for the frequency options you want to offer).