It appears that my federal tax return is a lower amount that what I was quoted by TurboTax. How can I get more information?

The IRS website should have information explaining why the refund issued was different then the amount on the federal tax return - https://www.irs.gov/refunds

Go to this IRS website for information on reduced refunds - https://www.irs.gov/taxtopics/tc203

Or you might have had any Turbo Tax fees deducted from a federal refund.  Then there is also an extra Pay with Refund service charge.