Learn English – What’s the meaning of “You get that much because that’s how much you get”

meaningword-differenceword-usage

I cannot understand the meaning of the phrase:

You get that much because that’s how much you get

It means: you receive that much because you receive that much?!

Like: Why A? Because A.

The full text is here:

The bishop and I were still meeting every Sunday. Robin had told him
that I hadn’t bought my textbooks for the semester. “This is ridiculous,” he
said. “Apply for the grant! You’re poor! That’s why these grants exist!” […]He had printed out the application forms, which he
gave to me. “Think about it. You need to learn to accept help, even from the
Government.”
I took the forms. Robin filled them out.
THE FORMS SAT ON my desk for a week before Robin walked with me to the
post office and watched me hand them to the postal worker.It didn’t take
long, a week, maybe two […]the mail
came
[…]I tore open the envelope and a check fell onto my bed. For four thousand
dollars. I felt greedy, then afraid of my greed. There was a contact number.
I dialed it.
“There’s a problem,” I told the woman who answered. “The check is for
four thousand dollars, but I only need fourteen hundred.”The line was silent.
“Hello? Hello?”
“Let me get this straight,” the woman said. “You’re saying the check is for
too much money? What do you want me to do?”
“If I send it back, could you send me another one? I only need fourteen
hundred. For a root canal.”
“Look, honey,” she said. “You get that much because that’s how much
you get. Cash it or don’t, it’s up to you.” Educated, Tara Westover (2018)

Best Answer

It's a cyclic, self-referential explanation, like "Why?" "Because".

He applied for a grant.
The grant is $4,000.
They sent him $4,000 because that's how much the grant is.
His need for only $1,400 is irrelevant, certainly to the people who made the grant.

"You get $4,000 because that's how much the grant is, $4,000"
is equivalent to

“You get that much because that’s how much you get."