Electric window wire length

Sorry, I have no idea.
I do recall someone posted a very good example of how they are fitted together so perhaps they mentioned the cable length?
Sometimes the search doesn't pick up what you search for, use multiple key words

There this article for the 308 but not sure it gives the right length for the 246, its a good starting point I guess

http://www.birdman308.com/service/windowservice/index.html

 

I have a spare Passenger's side from a 246 E and it measures 11.5'
8' of open loop and there are 6 windings on the OD 2.25" hub

 

Having restored/serviced similar regulator systems and replaced OEM(?) window cables on several 365 GTB/4s, my experience has revealed little to no consistency in cable lengths, locations of the pulleys or their support structures and I wouldn't be surprised if Dinos, which were constructed at same time period and by same "craftsmen", plagued with similar discrepancies.
Some individual cars have even had noticeable side-to-side variations in OEM(?) cable lengths, pulley locations and at times interesting(?) cable routing with additional "tensioners", etc, creating geometry so strange it's a wonder the windows moved/worked at all.
So basically, I'd recommend checking cable & pulley geometry first and, if necessary, modify/move pulleys, etc to locations better accommodating reasonably accurate window movement and then custom fabricating cables accordingly.