Put more money than I have on a budget leaves "Ready to assign" to 0

Hello everyone,

I have a question, I need to understand soething about YNAB. For the context, I am in France and I have a student loan to pay off. I already have the money to pay it off but I want to keep the money because I have a very good interest rate.

So I did a budget and n account for my loan. And every month I have assigned the amount I have to pay off in my budget (every month from now to the month I finish to refund my loan).

Now for other budgets, for example Spotify, I have to pay €10.99 every month. I made a budget for Spotify with a €10.99 target and assigned €10.99 to it.

Right now the "Ready to assign" section shows me that all money is assigned. But, if I assigned €11.00 instead of €10.99 in my Spotify budget, the "Ready to assign" section tells me also that all my money is assigned and not that I assigned more than I have.

If I put like €100.000.00 in my Spotify budget, YNAB tells me here that I assigned more than I have.

So my question is : What can I do to prevent false positive messages like this ? What did I did wrong ?

Thanks everyone for your answer !