Can you show us the cable route topography which needs the 818mls distance to require a 949mls cable?
If you think it fits exactly to globe theory it would fitting to provide evidence for that .
It's been answered before, it will be answered again.
Those are records of a ship in 1850 laying cable. They took their position with a sextant, let out 949 miles of cable and took their position again and found that they traveled 818 miles.
Lets list all the things that can cause that.
1. Sextants are not very accurate, and not continuous. They can only do spot checks and can only calculate their approximate location.
2. Wind and currents will cause them to veer off course and move in something other than a straight line. This will add to the length.
3. The floor of the ocean is uneven, this adds length.
4. The cable isn't going to be straight, it will also curve and bend as it falls to the floor, this will add length.
So there you go. I'm still not sure why I have to explain how dropping a cable onto uneven terrain is going to end up being longer than the surface traveled. That is pretty basic stuff. Get 100ft of string and try and see if it can reach 100ft if you have to drape it over a bunch of cars in a parking lot if you want to see for yourself.