A credit card issuer just raised your limit to $30,000, and your first reaction might be to ask for a smaller number. That can feel sensible if a huge limit seems like an invitation to overspend, but lowering it can create a credit-score problem before a mortgage application.
The reason has little to do with how much money you actually borrowed. Credit scoring models also look at how much of your available revolving credit you use. A larger limit can make the same balance look smaller, while a reduced limit can make that balance look considerably larger.
