TurboTax shows I should have gotten 1200 for 1st stimulus and 600 for 2nd. Didn't get the 1st. Got 307 for the 2nd. RRC shows $422. How do I get the full stimulus amt?

Sounds like you have a high income on your 2020 return. So you only qualify for a small amount more.  The Stimulus payments are really based on your 2020 income and AGI.  

If your AGI is over the limit, the amount of your payments is reduced by $5 for every $100 over the limit.  So, your credit may be a weird amount.  

Just because TT said you "should" have gotten you are given the option to enter what you did get in that same section >>>  

In TurboTax Online, to claim the Recovery Rebate credit please do the following:

1. Sign into your account and continue from where you left off
2. Click on Federal in the left-hand column, then on Federal Review on the top of the screen
3. On the next page titled Let's make sure you got the right stimulus amount, click on Continue
4. Follow the interview
5. TurboTax will determine whether you are entitled to any additional stimulus
6. Any stimulus amount remaining due to you will show as a credit on line 30 of your form 1040.