Should I omit work experience without fixed hours?

[muaddibs]

I worked part-time for over a year as a student and was paid hourly on a bi-weekly basis, but my hours fluctuated between 4-20 hours per week based on availability. I don't feel I need to add this work experience on my profile, but I've seen people talking about dishonesty based on omission here. Does it makes sense to just add a note about the work experience in a letter and send in a reference letter that shows I worked between 4-20 hours weekly, or should I just add it onto my profile as a 4 hr/week job?

Thank you.