Clarification on Z Axis nozzle height

I am reading the manual located at
http://download.lulzbot.com/TAZ/documentation/current/LulzBot_TAZ-User_Manual-ebook.pdf

On pages 93-94 it states…

The image to the right, in figure 5.3,
is the correct nozzle height. The nozzle should not be pushing down on the
print surface

However the image on the right is showing the nozzle pressed directly against the bed. The nozzle picture on the left is the one which is just above the bed. So which is right and which is wrong, is this an error in the manual and it was supposed to be the image to the left is the correct nozzle height.

I was always under the impression to take a card or paper. slide it under the nozzle, It should be just low enough that I can slide the paper out. If pressed down one more and it cannot be moved then i have gone too far. So basically lower it as much as possible where u can still slide it out.

Is this correct?

Your understanding is correct. Thing of an extruder just like a garden hose. If you turn on the hose but block the end, no water comes out. For an extruder, a blocked nozzle means that it starts chewing up the filliament instead. If you are too low you can even damage your heater bed tape. The other thing to keep in mind is that your nozzle wil get slightly longer at full operating temperature. if you calibrate it cold, you will be too close when it warms. I find that the little 150mm ruler that came with my AO-100 is just about the ideal thickness for the nozzle height, and it’s fireproof!

Too high from the bed and your extruded plastic comes out round, not squished at all, like an “0” The bottom of that “0” is a very small surface area compared to the overall width, so it doesn’t stick. You want it squished down a bit to adhere well and have the right shape. If you squish it too much then the layer starts too thin and causes issues above it.

Well unless I am reading it wrong the manual might have to get a slight correction. I used to have a regular CNC machine so I paused when I saw this but others may not and try to bring the nozzle directly onto the bed if they follow that instruction to make it reflect the picture on the right

After looking at the manual and the picture on page 93, I can confirm the manual linked is indeed incorrect. the two images are swapped and the correct height is on the left, not the right as specified in the text.

You are correct! We’ve changed that in later versions of the manual (2.0 and beyond) as the stock Slic3r configuration after setup has a Z axis lift before printing. Our current Slic3r configurations do not contain the Z lift on start. We’ve found that using the paper method of leveling the bed/setting the first layer height was easier, and changed the later manuals to reflect that. Here’s the current manual: http://download.lulzbot.com/TAZ/3.0/documentation/2013Q4/LulzBot_TAZ_3.0-User_Manual-ebook.pdf with page 53-54 containing the relevant section