auto grid survey waypoints are changed after klicking to accept. Why?

#### Issue details
When I set a survey grid wit auto survey grid, it does show the waypoints correct, but if I klick to accept, the waypoints are set different:

#### Version
Mission Planner 1.3.56 build 1.3.6672.30243

#### Platform
[ ] All
[ ] AntennaTracker
[x ] Copter
[ ] Plane
[ ] Rover
[ ] Sub

#### Airframe type
_What type of airframe (flying wing, glider, hex, Y6, octa etc)_
Quad X

I want this waypoints:

, but after klickint to accept, I get this waypoints. Why?

Reproduce the auto survey grid behavior in Mission Planner 1.3.56 build 1.3.6672.30243 on a Copter Quad X setup, comparing the displayed waypoints before and after clicking accept. The issue names no files, tests, or entry points; done means the accepted waypoints match the grid shown before confirmation.

Written by the indexing model from the issue text.