Unless the surviving spouse is designated as the beneficiary on the RRSP contract then the deceased spouse has been deemed to have received the fair market value of the tax deferred assets held within the RRSP. Income is also reported after the date of death to the estate or the beneficiary depending on the particulars. The T4RSP may be reporting that amount. You can confirm the nature of the reporting with the financial institution issuing the income slip. A surviving spouse may defer the income inclusion by transferring the amount to their RRSP as a refund of premium, using form T2019. There is income tax reporting on the T1 General for both the decedent and the beneficiary to effect that claim.
For your reference: RC4177 Death of an RRSP Annuitant URL:
https://www.canada.ca/en/revenue-agency/services/forms-publications/publications/rc4177-fact-sheet-d...
