Four degrees F. These are self-supporting cones, use these. I was consistently getting the cone on the left using a custom-programmed firing schedule to 2204F. However Orton recommends that the tip of the self supporting cone should be even with the top of the base, not the bottom. So I changed the temperature to 2200F and got the cone on the right. But don't assume your kiln fires cone 6 at 2200F, it could be much higher or lower, depending on your pyrometer.
Interpreting Orton Cones
Interpreting how high a kiln fired based on the look of the cones can be a much more complicated matter than it might first appear.
Devices that melt and bend in a ceramic kiln at specific temperatures. By viewing them through a peephole the operator can tell accurately what temperature the kiln has reached.
Plainsman Cone 6 Slow Cool (Reactive glazes)
Cone 6 Drop-and-Soak Firing Schedule