"I amended my return to add $4619 as a1099-R IRA RMD for 2018. The TurboTax amended return shows that my Gross Adj Inc increased by $7828. I don't understand. Why? "

If you are also receiving social security, the higher your other income, the greater the percentage of social security benefits that are taxable.  And several other benefits and credits are based on your adjusted gross income.  Increase your total income could affect many other calculations on your tax return.

Thanks! That was it. The $4619 made another $3209 of Soc Sec taxable for a total AGI increase of $7828. Still sucks! :(

Answered in comments.