There's a 0% chance this hasn't been reported but I couldn't find it 

If you change the delay on a repeating commandblock while it is running it will often continue using multiple instances  of the new delay until allowed to complete a full cycle while not active

Steps to reproduce:

Place a repeating commandblock with /say hi

And a separate one with /say how

Active the commandblock that is /say hi with a delay in ticks of 300

Activate the commandblock with /say how with a delay in ticks of 2400 

Deactivate /say how 

Set delay to 1200

Activate /say how

Deactivate /say how 

Set delay to 600

Activate /say how

Deactivate /say how 

Set delay to 300

Activate /say how

Wait over two minutes and read chat

Expected result hi's and how's should be equal in proportion 

Observed result about 4x as many how's as hi's