PLA Scalloped Lines

Nozzle too high.
Note that it (the filament) is not pressed in place.

You should have seen the famous @tesseract first layer pic by now, and that, is not like yours

 

Don't confuse the thickness of the (first, or any) layer with the initial starting height for the first layer. The thickness of the first layer is how much filament the extruder will be putting down (not where it starts Z-axis wise).

Your extruder needs to be very close to the bed initially (a few tenths of a MM) which is where the 'start with a sheet of paper' advice came from for those of us who manually level. EVEN that was too high, but it was a nice starting point to work down from. If it is AT the correct starting height then it will look like @tesseract famous photo (whether that was achieved via auto-level or manually).

If you have an auto-leveling one, I'll let someone who uses that comment, BUT the problem is still the same regardless of how it needs to be sorted

 

They are not directly related for this discussion. The Z offset does NOT control the thickness of the first layer just the Z axis point at which the nozzle will start putting down filament. In your picture that point is too high off of the bed.

Try lowering the Z offset and doing another test (you need only watch the perimeter as @tesseract describes) since that alone is enough to see if you are correct. Once your first layer (or the perimeter) looks correct you have identified the starting Z offset you need. Again, this is theory for me as I do NOT have an auto-leveling robo, in my case the Z offset is controlled manually.

P.S. the complete layer is not put down in a single pass of the extruder normally either, but multiple ones...

 

In some software there is a setting for z offset that you found and it will affect the first layer but there is another way to do it which is faster it is to edit the gcode directly. Doing it this way means you do not have to reslice the print each time since this setting has little to do with the actual print itself but is more a start point.

If you choose this route you should be familiar with the Gcode and if you are you will see a G29 command this is usually at the beginning right after the initial homing of the print right after the G29 command(the one for autolevel) is where you can place code to this offset.

This section is usually found in the start up gcode block in the slicer also, so if it is added in that block it will be done automatically as well but if you do do it this way then the z offset in the software slicing section must be set to ZERO as it will conflict and I do not know which would take place.

The code for this is as follows:

G29 ; start autolevel routine
G1 Z0.5 F2400 ; adjust for offset
G92 Z0.00 ; set offset


This block sets the offset to .5mm and will need to be adjusted to match your printer and prints
the command looks like this
G1 Z(your offset value) F2400 ; adjust for offset
G92 Z0.00 actually is the setting command

This says in English
autolevel
raise Z by .5mm at 2400 speed
set z to 0.00 based on its current position so in effect 0.5 now becomes 0.00 and it is off set for the entire print

this value will need to be adjusted to meet your needs but can usually range from -1.00 to 1.00 the goal as @mark tomlinson mentioned is to get the first layer at the pest height here are the pics he was talking about.One shows what you should strive for the other explains some different conditions and what happens or is seen



the first picture is a solid 4 based on the second image