Canon MX720 Series Online Manual page 103

Note
To access other available functions, use the mode buttons or the MENU button.
For (B) (lines are missing or horizontal white streaks are present) in the pattern
(2), or in both the pattern
(1) The cleaning is required. Select Also B, then press the OK button.
The cleaning confirmation screen will appear.
(2) Select Yes, then press the OK button.
The machine starts cleaning the print head.
Cleaning the Print Head
Note
The total number of sheets printed so far is shown in increments of 50 sheets on the printout of the
nozzle check pattern.
(1) and pattern (2):
(1) or pattern