Last year I was told that I could use the numbers from a previous year if it would benefit me. I did that and now IRS wants me to pay on last year's numbers.

Not sure what you are referring to or what numbers you used last year.  There was a provision to allow people to use a prior year amount for the purpose of calculating earned income credit.  Is that what you mean?   And has the IRS now sent you a letter about that?   We are in the dark----TurboTax does not receive any information from the IRS after you file your tax return, so no one at TT knows about anything the IRS is telling you now.

I RECEIVED A LETTER FROM THE IRS/STATE

TurboTax does not receive any information from the IRS or your state after your return was filed, so no one at TurboTax knows about a letter you received from the IRS or the state.

(what the letters from the IRS mean)

I GOT A LETTER FROM THE IRS   

https://ttlc.intuit.com/questions/3605673-i-got-a-letter-or-notice-from-the-irs

I AM BEING AUDITED

If you purchased Audit Defense:

https://ttlc.intuit.com/questions/2924451-i-bought-max-or-audit-defense-and-now-i-m-being-audited

AUDIT SUPPORT

TurboTax has a special phone number for help with IRS/state tax letters, which will be easier than going through regular Customer Support.   At the page below, click on the blue button that says "Get Help from TurboTax Support".  Then it will ask you what tax year is your letter.  Then it will ask you what the letter concerns. Then it will show you the phone number during posted business hours.

https://support.turbotax.intuit.com/irs-notice/audit-support/