From the attached picture:
So L1-L2=1.033
It seems that you round of the above result to 2 significant figures.
So S1P=10.42 , S2P=9.38
and you round off |S1P-S2P} from the above |1.033| value, so you get 1.03

If you want to get 1.04 you should calculate difference from the round-off values instead.


double dv;
public float  roundoff(double v){
else if(v<0)dv=-0.5;
else dv=0;
return (int)(v*100+dv)/100.;

roundoff(L1) will give you 10.42
roundoff(L2)will give you 9.38
roundof(L1-L2)will give you 1.03
roundoff(L1)-roundoff(L2) will give you 1.04

This is an opportunity to teach students about the meaning of significant value (the last digit might be off).

I would not change the above result, but I will ask student why it is off (provide opportunity for student to think about this problem).
It could have more education value if we take the opportunity to invite student to think/learn:
There is always error due to numerical simulation.
And the physics experiment always contain error, too! It is a nature of physics.