Confused

Hello! I've written in here before, but I'm just slightly confused about something.

If you know my journey, I applied for SSI in late July 2025 and was denied and appealed on reconsideration in October for f the same year. I was approved for SSI December of last year, and now somehow I was approved for SSDI?

For reference, I am 20. I didn't think I had nearly enough work credits. It says "social security (disability)" as "active" as well as SSI and the amount I receive every month under it. I thought two things were true: 1, you had to have 40 work credits and 2, it needed to be 10 years that 10 were earned. I noticed that for younger people (under 24?) had to earn 6 in three years, which would mean I somehow did so.

I have not received the notice as the decision was made yesterday. How would this affect my SSI? Is this common? I saw in a previous post that it will just even out to the max of the SSI, which would make sense. Is there anything I'd need to do after that?