[rawling]

I couldn't figure out the justification for middle C being on a ledger line, and then the D above it being higher up, but on the higher of two ledger lines.

[projektfu]

It follows the same pattern in the middle of the staff. Between the two bottom lines is another whole step represented by a ledger line.

I thought it was odd too but I can see how it makes sense, given that they want to unambiguously represent half steps.