After you complete IOE, you will bid and fly a green line. You are considered "green" if you have less than 75 hours in the aircraft. FAR 121.434 requires that you have 100 hours in the aircraft within 120 days of your check ride. The green line is a full month of flying that will allow you to take a significant step toward the 100 hour requirement. You will probably block (log) about 80-85 hours of flying during your green line. Coupled with your 20-25 spent on IOE, you will have the requirements of FAR 121.434 complete.

Basically because of your junior status, you will not be able to hold a regular line of flying after you complete IOE. Mesaba will designate "green" lines in the monthly bid package as required for green pilots to bid and be awarded a line of flying to gain experience. After your green line, you will go back to bidding what you can hold with your seniority.