I hope you have read the tutorials already and I'm not wasting key strokes.
Look at your existing plot, it should have the format of:
numericID_0_EndingNouce_StaggerSize
Your your next file with the following parms:
numericID_EndingNouce_NumberToAdd_StaggSize
Eg: first file is: 123123123_0_344000_4000
New one should be 123123123_344000_#####_4000
for #### Put in the number of Nouces, You can calculate the number of nouces if you know the number of GB you wish to use. The formula is GB * 4000, so to add 1TB use the number 4000000. Always leave a little headroom in your calculation, you could get rounding due to stagger size, 5% under sizing is typically safe.
HTH,
-IceBurst