TPG is an online tax submission outfit that deducts their fee from your refund.
TPG is Santa Barbara Tax products group. They are the servicing agency of your tax refund when you choose Pay with My Refund.
A refund may be smaller than expected for one of two reasons:
Did you make a mistake when it asked if you received the $1400 per person stimulus checks last year? Sounds like your difference is exactly 2 x $1400. If you really received that payment but forgot and said on your tax return that you did not receive it, the IRS took it away. You cannot get it twice. The IRS will send you a letter of explanation.