A Form 1099-R for a distribution from an IRA should never have an amount in box 5. This is almost certainly a distribution from some kind of account other than an IRA and I expect that IRA/SEP/SIMPLE box on the From 1099-R is not marked.
Yes, the amount in box 5 is the amount of this distribution that is not taxable. The taxable amount should be present in box 2a, the difference between the amount in box 5 and the amount in box 1. (I'm assuming that there is no amount shown in box 6.)
When you enter this Form 1099-R, be sure to enter it accurately, with the state of the IRA/SEP/SIMPLE box on TurboTax's 1099-R matching that of the Form 1099-R provided by the payer. Since this is apparently not an IRA, this box should not be marked and TurboTax will include the gross amount from box 1 on Form 1040 line 16a or Form 1040A line 12a but include only the taxable amount from box 2a on line 16b or 12b.
