Question about: Claim of right repayment over $3,000

I wasn't able to understand the deduction mentioned in the Help as "Claim of right repayment over $3,000".
It says something as if I paid more than $3000 last year, but I paid back this year, blah... Wasn't really able to understand if this applies to me.

Could you explain a bit better the concept behind it, so I understand if this applies to me or not?

Thanks!