No one here can tell you why your return was changed which caused you to receive less refund. Only the IRS (& State, if any) would know what they changed. You will be receiving a letter explaining the changes to your return and what you can do if you don't agree with the change. The letter can take 6 to 8 weeks to receive.
You can also call the IRS for more information.
IRS Toll-Free Help
You may call 800-829-1040 with any Federal tax questions.
