Fret distances for chromatic semitones are with good precision what could be expected for meantone; diatonic fret distances are less than expected for meantone. If the tuning was supposed to be meantone these tangents had to be bent outwards.

The 4-foot (A1 - g#) is a later addition. All the unfretted bass keys have a 4-foot string, but also the first two fretted keys (f-f# and g-g#) As the fretting distances are calculated for the 8-foot string lengths the shorter 4-foot strings will give a semitone which is much too large and totally out of tune.