How to translate MFC from logical to physical coordinates?

Question

C++ / C#

Suppose there is a text that is specified by the LOGFONT
structure. It is written that it is specified in logical units, as I understand it, only the mapping mode affects the transfer from logical to device, and it is also possible to shift the coordinates, i.e. if I don't apply anything then logical unit= device unit?
And what should I do if I use the mapping mode, for example, I compressed Y by 2 times, how can I then pull out this information when choosing a font size?
I draw directly on a 1:1 image, which I then save to a file and I need to set the text height in % of the image height.
And how is this formula explained?

lfHeight = -MulDiv(PointSize, GetDeviceCaps(hDC, LOGPIXELSY), 72);

It is still not clear what is meant bydc.GetDeviceCaps(LOGPIXELSY)

LOGPIXELSY
Number of pixels per logical inch along the screen height. In a system with multiple display monitors, this value is the same for all monitors.

What means

Number of pixels per logical inch

What is logical inch? Aren't logical coordinates abstract?