TurboTax generated my total capital gains value to be much higher than my total investment income. Is this a TurboTax error?

If you imported the forms, you will need to check the values. You may want to delete them, clear  cache and cookies, and then enter them again. You may want to change your browser as well. 

Double check that you don't have other capital gains, say from business, that may be affecting your totals.

"total capital gains value to be much higher than my total investment income."

If you consider investment income to be dividends and interest, this is not uncommon.

@marcnorm