The first column corresponds to the global time step up to which the time step indicated in the second column has to be used.
As example, let's say that a user wants to perform a calculation with time step 0.5s during 150 time steps, then 50 time steps of 10s each. Then the table should be filled as below:
150 0.5 "First 150 times step of 0.5s each"
200 10. "50 more times step of 10s each"