Confuse:Some waypoints are missing after RC7 set save way point and the Smart RTL mode

Hi guys

I set the RC7 channel to save the waypoint.After this I drove the rover for a while and saved about 30 waypoint.When I download the waypoint form rover.Mission planner showed just 12 waypoint be downloaded(I try to drive the rover under auto mode to prove those 12 waypoints and proved this is real).I wanna know why some waypoints was missing?Those missing waypoints are the end part of the path(may be 40%-100% of the whole path).
But the interst is when I set servral waypoint(Less than 10 maybe).I can download all of it.

I’d like the rover return to home follow the path.for example.the rover drive from waypoint 1-2-3-4to20 and return as waypoint20-19-18-17to 1.The smart RTL mode can do it?I’v a little confused about the introduction document of this mode.

I’m not a English native speaker.Sorry for my terrible English :sweat_smile:
Thanks all of you