It's possible that the increase in your salary caused you to move into a higher tax bracket, which could result in a higher tax liability. This means that a larger percentage of your income is being taxed at a higher rate, which could explain why your after-tax pay increased by less than the amount of your raise.

It's also possible that other factors, such as changes in the tax laws or in your withholding, could have affected the amount of tax you owe.

Without more information, it's difficult to say exactly why your after-tax pay increased by less than the amount of your raise. I recommend consulting with a tax professional or doing some research on your own to better understand the tax implications of your raise.