TLV is target line value. Think of it as a finish line that the award engine tries to cross. In the bigger scheme of things TLV is a number within a maximum and minimum credit window range.

Generally your monthly schedule must fall within the credit window. The award engine asks itself a question each time it puts a trip on your schedule "Have I exceeded the TLV?
If yes, is the months schedule within the credit window? If yes, Line
is complete..."

There is of course more logic if the answer is no to any of the questions, but that is a simplistic explanation. The bigger point I am making with all this is that the TLV can be thrown out IF you set a PCT (personal credit threshold) which essentially acts as your personal TLV-- but it must fall within the credit window set by the company... PCT has its own set of caveats...

More than you wanted to know I am sure...