Student maintenance loan seems incorrect?

I’m posting on behalf of my boyfriend because I’m anxious and he doesn’t have an account here. He will be calling student finance today but I thought any advice here could also help.
So my boyfriend started university and had to leave due to health problems in 2023, he has now reapplied and sent off all of the appropriate forms and because you can get a full 4 years of funding, everything seems to be ok. I don’t think that him leaving and rejoining a different uni is apart of the problem.

So he applied through the post and at the same time sent off a 15% decrease form. His parents would initially have claimed to be making 36k but his 15% decrease form would claim just around 28k, possibly even a bit less.
His letter came back and said that his maintenance loan would be only just over 7k. This would not even cover our rent.
Now we are confused for two reasons. Firstly the calculator would suggest that he would get enough to cover rent at the very least and whilst I understand that the calculator isn’t the most accurate I am also baffled because my family would have claimed to have a higher income than his and yet I am going to be receiving £8,980.
I will be not far off receiving £2,000 more than him but there is simply no way that his family would have claimed to have a higher annual income than us especially with them having sent in the more than 15% decrease form which as I said, was sent in at the same time as the rest of his student finance application as he applied through the post.

Any advice or explanation is welcome, it seems like a quite drastic miscalculation?

I have also sent in a 15% decrease form but the student finance form that outlines my entitlement does not take that into consideration yet, so I am anxiously awaiting finding out how much I will actually be receiving but I know as the baseline I will be able to cover my part of the rent. I know that because I applied online and then sent off a 15% decrease form separately that they are simply calculating my loan a bit slower and should be making amends to it relatively soon (I hope).

I thought maybe something similar was the case for my boyfriend but as I’ve said a few time now, he sent all of the forms in at the same time, in the same envelope!! I can’t see how, even if for some reason the loan he’d get for the 23/24 tax year was simply lower than expected, why the decrease for 24/25 wouldn’t have been taken into consideration at the same time. This loan is definitely too small for someone with a 28k annual income.