I've been trying to make a timer that starts from 0 then counts down at 9 to 0. I've been struggling to make it. I made state tables and diagrams and for the flipflops, but when implementing to a simulator, it just doesn't give me the output I want.

I've tried making the don't cares (10-15) as 0 but still doesn't work.

Here's the state diagram:

Here's the state table:

I followed the kmap results in the simulator but still can't get it to work.