There are a couple different reasons you might be seeing an amount doubled in a summary while using the TurboTax Online program.
You may have entered your RPP Contributions from your T4 Box 20, then again in the RRSP Profile by mistake. If you did this, however, the amounts will show on two different lines as two separate amounts.
You might be seeing a double amount of Registered Pension Plan Deductions if you used the CRA Auto-Fill feature to import your tax slips, and then entered the same slips manually. This happens often and can be easily fixed by returning to the T4 Slip summary page and deleting one of the slips.