Proper meaning of status codes?

[ytbe.use3]

I saw the status codes under docs section and I want to make a clear meaning out of them. Can someone help me?

status codes on exit:
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-2 = gpu-watchdog alarm (I am assuming this triggers when there is an issue with running hashcat with GPU. Correct?)
-1 = error (When is this triggered? When proper parameters are not provided?)
 0 = OK/cracked
 1 = exhausted
 2 = aborted (Triggered with Ctrl+C?)
 3 = aborted by checkpoint (When is this triggered?)
 4 = aborted by runtime (How diff is it from status code 2?)