The other data in your account includes any backups (seen on your phone in Settings>iCloud>Storage & Backup>Manage Storage, under Backups); as well as the other data you are syncing with your account such as mail, contacts, calendars, notes, reminders and iWork documents, all of which you can see in the apps on your phone as well as by going to icloud.com on your computer. Based on how large your usage is, I suspect you still have backups stored in your iCloud account.
As mentioned, you can go to icloud.com and start deleting your data (such as deleting your contact by selecting a contact, pressing Control-A to select all contacts, then tapping your Delete key) but when you do this, they will also be deleted from your phone and any other device syncing with your account. I assume you don't want to end up losing your contacts, calendars and other data.
If you really want to start over, you could always go to Settings>iCloud, tap Delete Account, choose to keep the data on your phone when prompted, then set up a new iCloud account with a different Apple ID, turn your data syncing back to On, and when prompted choose Merge. Note: you can only create a maximum of 3 iCloud accounts on each of your devices.