I believe that Kim would be concerned about moving to the next tax bracket because the more money you earn in a year, the higher the income tax, and oftentimes groups of people that make anywhere from someodd-thousand to someodd thousand get taxed so much, and once you move up out of that range, you'll get taxed more, leaving you less money in your bank account that you worked for.
Fingers crossed that I helped you! :)
