Reply To: GREP Expression to find specific range of characters?

How about this

(?<=[^\d{6}])(.{25,30})(?=)

That will find a string of any characters inbetween the first 6 digits and the two tabs

The amount of characters it finds is between 25 and 30

In your paragraph style – include a GREP styles – then add new GREP styles for 25 to 30, 30 – 35, 35 – 40 etc.

And create a character style for each one which gives it an increased negative value for the tracking