If one has some speakers at 10 feet away and some at 20, the system would need to delay the signal to the closer speakers the equivalent of 10 feet of sound-though-air travel time. If your system were to measure these speakers as 15 and 25 feet away respectively, the delay given to the closer speaker, compared to the more distant speaker, would be the same as if the system had measured the more accurate distances of 10 and 20 feet respectively.

If your mains are 2 feet further from the measurement position than your center, do the system distance values reflect this? (Of course if your mains and your center are not designed as a set, or if the mains experience more electronic/acoustic delay than your center, they may measure with a larger difference in distance than would be otherwise.)