Hi, I let the TurboTax access my TD Ameritrade account and download automatically the numbers, but ne numbers look slightly wrong. why is that?

TurboTax recommends you review the import data to your 1099B source document to ensure all the transactions imported correctly.  Many times the import might be incomplete.  Make sure and review those entries to your 1099B received from TD Ameritrade and make any changes.  Additionally, brokerage firms have till 2/15 to issue your 1099s.  I would recommend waiting till mid-February to file your returns.  The IRS is not accepting or processing tax returns until 2/12 so there is plenty of time to get it corrected.  

You also might try deleting the imported data from TD Ameritrade and importing again on a date closer to the time the IRS is starting to accept returns in the middle of February.