Why and what is host login?

The login screen of command-line with virtual machine’s memory size <= 512MB says:

-If this is a virtual machine, ignore any “host login” below.
Do not…

what does it mean?

If I do ignore host login below, how can I login to Whonix?

Just follow the instructions on the screen. This isn’t difficult.

Instruction tells me not to host login, but the username I enter in console is for the host login?

Don’t overthink this. Don’t make it a big deal. For real.

Just enter user, press enter. Done.

Should take less than 1 minute to read and follow instructions. Everyone else managed. Just forget about the part you don’t immediately understand.

It’s just a help text. Don’t let is confuse you.