Basic understanding of op amp circuit
The resistors at the non-inverting input are for the bias current compensation. In a non-ideal opamp the bias currents flowing into the inputs are non-zero.

Parallel resistance of R7 and R8 is nearly equal to the parallel resistance of R2 and R3 (1485 Ohms).

The matching in this circuit is not correct, because the output impedance (R1) of the source is not taken into account.
(R1 + R2) || R3 = 1973 Ohms. A better choice for R7 and R8 would be 3900 Ohms resistors.

For more information on the input stage and bias current compensation take a look at this app note.