What your quoted statement is missing is the the change in definition of a permitted aircraft. LOA 46 changed the definition of permitted aircraft from "certificated" to "configured."

C2K

Section 1.B.17. “Permitted aircraft type” means:

c. one of up to 57 jet aircraft certificated for operation in the United States for 70 or fewer passenger seats and a maximum certificated gross takeoff weight in the United States of 85,000 or fewer pounds. This number (57) will be increased to a maximum of 75 at the rate of one aircraft for each increment of 10,000 scheduled block hours of Company flying in the previous year above the scheduled block hours set forth for that year in the block hour plan set forth in Section 1 E. 1., (i.e., prior to any resets under Section 1 E. 5. or 6.).

LOA46

Amend Section 1 B. 17. c. to read as follows:
c. one of up to the number specified in the chart below jet aircraft configured with 70 or fewer passenger seats and certificated in the United States with a maximum gross takeoff weight of 85,000 pounds or less (“70-seat jets”). This number of permitted 70-seat jets will be increased to a maximum of 150 in increments of one aircraft for each unit of 10,000 scheduled block hours by which the number of scheduled block hours of Company flying in the calendar years 2005 or later exceeds 1,950,000. (Examples: If in 2006 the Company operates 2,017,000 scheduled block hours of Company flying, then in 2007 and thereafter the number of permitted 70-seat jets will increase to 13 1. If in 2007 the Company operates 2,044,000 scheduled block hours of Company flying, then in 2008 and thereafter the number of permitted 70-seat jets will increase to 134.)