It took me a bit of digging to figure this out. So what you have to do is go to /local/ftbu/ranks.json. Once there you'll be presented with a config file that looks like this:
{
"default_ranks": {
"player": "player",
"op": "op"
},
"ranks": {
"player": {
"parent": "builtin_player",
"permissions": [],
"config": {}
},
"op": {
"parent": "builtin_op",
"syntax": "<&2$name&r> ",
"permissions": [],
"config": {}
}
}
}
Inside of the config curly brackets for player (or any other rank you've created for that matter) type in the following:
"ftbu.claims.max_chunks": <amount>,
"ftbu.chunkloader.max_chunks": <amount>
It should look like this:
{
"default_ranks": {
"player": "player",
"op": "op"
},
"ranks": {
"player": {
"parent": "builtin_player",
"permissions": [],
"config": {
"ftbu.claims.max_chunks": 1000,
"ftbu.chunkloader.max_chunks": 1000
}
},
"op": {
"parent": "builtin_op",
"syntax": "<&2$name&r> ",
"permissions": [],
"config": {}
}
}
}
Note that this number can be changed to anything up to a maximum of 30000. Also make sure ranks are enabled on your server for this to work properly (I believe they are enabled by default). Sorry for the wall of text but I hope this helps!