Bracketed number in user list description

[NTTScooch 0]

I'm using ApexDC++ v1.0.1 and I've noticed that for some users, their description is prefaced by a number in brackets as seen in the screenshot. What's the purpose of this number? I think I've noticed this in other clients as well but I've never known what it means.

[Satan 1]

Thats the number of free slots a user has.

[NTTScooch 0]

Thats the number of free slots a user has.

Really? Thanks. Quite simple.

[Zlobomir 3]

You can enable/disable these values for yourself from File>Settings>General Info> Limiter and Slots. Some hubs enforce showing limiter in description.