Try this version
If(
IsNull([Started]) and Today() < [Start], "Past Start date but not started,
[Active Dif Calc]>=7,"LT7",
[Active Dif Calc]>=1,"LT1",
[Active Dif Calc]=0, "N/A")
You have asked for the result to be "N/A" if the date that the job was started was equal to the date the job was supposed to start, and then also asked to have it read E1 if the job was started a few hours early but that could be on the same day as it was supposed to start, so that would calculate to "N/A".
ie the N/A and E1 logic you have asked for does not make sense to me. You may have to illustrate with an example.
