what is the meaning of flags in Digiinfo?

Hi 
When using Digiinfo to examine the touchpad output, the ‘buttons and flag’ column has four types of flags: tip, confidence tip, confidence, and blank. What do these four flags mean respectively? How are these flags generated?
The flag is "Tip" when I touch the touchpad with a palm.
The flag is "confidence tip" when I touch the touch pad with a finger tip
The flag is "confidence"　when my finger leave the touch pad.
The flag is blank when no object touches the touchpad.

How does Digiinfo determine the flag??