How is letter-spacing distributed?

All <p> elements have 50px of letter-spacing applied. For green spans, 100px of letter-spacing is applied.

Span surrounding middle character with background set to red:

ABC

AבC

אBג

Span surrounding all but the first and last characters in the line:

AB123C

Aב123C

אב123ג

Span surrounding all but the first and last characters in the line, letter-spacing increased within span:

AB123C

Aב123C

אב123ג