Canon PIXMA G620 Printer - Manual (Page 321)

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Cause
The remaining ink level in one of the ink tanks may have reached the lower limit line shown on the ink
tank.
What to Do
To check the remaining ink level, visually inspect the remaining ink in the ink tank.
If the remaining ink level is below the lower limit line, refill the ink tank with the corresponding color of ink
by following the printer's instructions.
Refilling Ink Tanks
If printing is continued when the remaining ink level is below the lower limit line, the printer may consume
a certain amount of ink to return to printable status.
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