Why am i getting back so much less than turbo tax estimated? According to the IRS, I'll be receiving a refund that is much less than was estimated.

I have a simple return. I'm single and only claim myself. In checking the status of my refund, I was informed that it took longer than expected because it had to be corrected. I'm now receiving quite a bit less than the system has me receiving. This is my first time using Turbo Tax. Is this how it usual goes? Thank you.