You can calculate what we would expect the capacitance of C2 to be in order for the total capacitance to be 50 femtofarad. Calculate the expected capacitance (with uncertainty) and compare it to your measured value. You may neglect the uncertainty in C1 and C3 for this calculation.

Calculate the expected charge on and potential difference across each of the three capacitors. You may neglect the uncertainty in C1 and C3 for this calculation. Compare this to the total charge reported by the simulation, and the voltages you measured. Are they the same?