I did not get my first stimulus payment of $1200 but did get the $600, when I filled out TT recovery credit, it only gave me a credit of $385 why not the full amount of $1200?

Was your 2020 income above the threshold?   Eligibility for the recovery rebate credit per the IRS:

A1. Generally, if you are a U.S. citizen or U.S. resident alien, you will receive an Economic Impact Payment of $1,200  ($2,400  for a joint return) if you (and your spouse if filing a joint return)  are not a dependent of another taxpayer and have a Social Security number valid for employment and your adjusted gross income (AGI) does not exceed:

• $150,000  if married and filing a joint return
• $112,500 if filing as  head of household or
• $75,000  for eligible individuals using any other filing status
  Your payment will be reduced by 5% of  the amount by which your AGI exceeds the applicable threshold above.

You are not eligible for a payment if any of the following apply to you:

• You may be claimed as a dependent on another taxpayer’s return (for example, a child or student who may be claimed on a parent’s return or a dependent parent who may be claimed on an adult child’s return).
• You do not have a Social Security number that is valid for employment.
• You are a nonresident alien.
  The following are also not eligible: a deceased individual or an estate or trust.