[Wentys]

Playing Just Declare with the basic 2/1 robots, I got this hand and auction, and the pop-up explanation that South's 3D rebid showed 18-22 total points.

Both vulnerable. East dealer. Bidding: p;1H;2H;p;2S;3D;p;4H;p;p;p
S: _
H: AKJ954
D: AK32
C: A52

Is it the new second-suit bid at the 3-level that shows 18+ points?

This is a 19 HCP hand with a void, and is a 4 Losing-Trick-Count hand. What about a 2C opener? What are robot rules for opening 2C?

thanks

[helene_t]

Robots tend to require enormous strength for voluntary rebids. Imo 3d should just show two chunky 5card suits or so and doesn't show points.
Robots are reluctant to open 2cl.

[Zelandakh]

The meaning for 3♦ in an auction like this is dependant on the meanings of X and, most importantly, 2NT. I do not know the GIB system but I would guess it uses 2NT to cover competitive hands with a side minor, leaving a direct 3m call to be constructive. There are multiple reasonable structures here so you need to look at all of the options to understand how it all fits together.