Revolving utilization and installment utilization are computed completely separately.
If you see a credit monitoring tool (like Karma, etc.) refer to your "utilization" (typically giving it as a percent) it is without a doubt refering to revolving to your revolving utilization -- it has nothing to do with your installment accounts.
The FICO 8 and FICO 9 models do indeed, however, look at your open installment accounts and compare the amount you currently owe compared with the original loan amount. The concept is much the same as revolving utilization, though as I mentioned the two things are computed separately. Many people here on the forums call this "installment utilization" -- others may call it B/L ratio (balance to original loan amount).
Can you tell us the current balance and original loan amount for each of your open loans? Something like this:
Loan 1. Balance = ____ Original Loan Amount = ____
Loan 2. Balance = ____ Original Loan Amount = ____
Loan 3. Balance = ____ Original Loan Amount = ____
etc.
Indicate which of those are student loans and of those SLs which are in deferment.
Also curious to see your revolving accounts, again like this:
Card 1. Balance = ____ Credit Limit = ____
Card 2. Balance = ____ Credit Limit = ____
Card 3. Balance = ____ Credit Limit = ____
etc.
If you can show us a screenshot of the NFCU screen (with you say is claiming that you have a negative utilization) that would be interesting.
