Q: Time Machine error

Yeah fun nonsense that TM comes up with.

How much actual space shows on the TC from the disk tab in airport utility?

I would use a few of Pondini's tools.. It is a bit dated but still useful.

1. Verify your Mac OS disk and the backup.

A5 here. http://pondini.org/TM/Troubleshooting.html

2. Reset TM

A4 in same place.

In the end the fix is often to wipe the TC disk and start over. TM can be a bit dodgy especially if you upgrade installed a couple of OS without a clean TM backup.

TC is Time Capsule.. this discussion area is Time Capsule.. so most people are used to seeing TC for time capsule.

TM is Time Machine .. which is NOT this area.. it is part of your OS. If you use external hard disk it really should go under El Capitan or whatever OS you run. Although we end up answering more Time Machine questions than Time Capsule.

Do you have a Time Capsule.. or are you backing up to an External drive.

Your only statement of information is you have 2TB which is standard size Gen4 and Gen5 TC.

A4 and A5 I gave with a reference which apparently you did not click.. so here is the references directly.. please click the link.

http://pondini.org/TM/A4.html

http://pondini.org/TM/A5.html