Injection start time


here The injection start time is after the second day.

What should I do if I want the injection start time to be always 8 am? (Instead of starting the second day).
I mean The injection start time is always the same as the start time of the simulation.

inj_start_time = 2*48; % after day 2 (Dt = 30min)

I changed the above line and put

inj_start_time= 8 


inj_sc=[randi(G.NodeCount,Ns,1), max_inj_conc*rand(Ns,1), 8, randi(inj_duration,Ns,1)]; % Injection location, magnitude, start time, duration 

but the result was not 8 am.

I have another question too, can someone help me?, What does this ((Dt = 30min)) half hour mean?

Thanks in advance!