friend limit

I have a problem. When I type "/f list" there is (2/ -1) friends. When I try to add someone there types "that you have reached limit of friends" . I deleted Cubecraft server and added it again, but it doesn't work, so I deleted Minecraft and installed it again, but it still doesn't work. Please...

I used to have 150 friends when I was stone rank. I got lapiz rank and deleted some of my friends, Now I have 56 friends. I think every rank should have unlimited friends so that you can be friends with more than 30 people (for me but for obsidian rank its 100+ I think) I would really like more...