totalPressureDrop.m in ErgunTestMPI_*

Hi
One question:
I found the difference of defination in totalPressureDrop.m of Tend in ErgunTestMPI_cgs with ErgunTestMPI_restart
In ErgunTestMPI_cgs is :
Tstart = 0;
Tend = t_sim(length(t_sim));
deltaU=(Uend-Ustart)/((Tend-Tstart)/timeStepSize);
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In ErgunTestMPI_restart is :
Tstart = 0;
Tend = t_sim(length(t_sim))
Tend=0.1
deltaU=(Uend-Ustart)/((Tend-Tstart)/timeStepSize);
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You know in both cases, the simulation time is same, t = 0.1s. When I try to delete the Tend = 0.1, I have a error when plot the octave such as time must match.
Can everybody explain these?