Do teachers commonly know their contact hours?

So this has happened to me many times when teachers are talking how many periods they teach instead of their contact hours. I ask them how many hours they teach per week and they tell me the number of periods instead. I have never pushed the topic because obviously its not a big deal but then when they hear i have 19 contact hours they respond with "oh I wish! I have 35 lessons a week!" But I dont know how long your schools periods are so I have no clue what that means.

It has happened so often that I wonder if teachers assume I teach 19 lessons a week.

Also, im an entire school homeroom teacher so im across 3 different timetables and each with different lengths of lessons.

When speaking about our weekly schedule is using contact hours or lessons more common?

This is my third school that this has happened where other teachers respond only with the number of lessons and im starting to wonder if im wrong here for using hours taught and not lessons.