Hm, I have never, ever needed to enter a "second object" on that rule.
I can't actually imagine what use that would be, or why. The first object is obviously(?) the pad being poured around, and that's pretty much sufficient.
A test is in order.
It seems the second object is the polygon itself:
This is in AD16, which should behave identical to current version, in terms of extant design rules and query matching.
I sorted through most every type of object I can think of, which excluded a few thousand, leaving just 46 in this example. Only the polygons (or the hidden regions they're composed of) matched.
Here I've broken it down to exclude a single polygon, which you can see has the expected effect. Excluding the components or pads has no effect here.
Just to prove polygon doesn't apply in the first case, I excluded everything but the polygon in question; now nothing pours direct-connect (including the targeted polygon itself).
This is confusing, because the "Test Queries" button indicates that, pretty much anything in the query, is applicable. It seems like it may be a bug, as only non-polygon net objects should count for the first, and only polygons for the second. (Perhaps this has been improved since.)
Thanks, I shall add this information to my toolbox! (I doubt I'll use it, ever -- I've not needed this question asked before, and likely won't again -- but it's now there, just in case, and you never know.)
I suspect the most useful application would be, you have a great many polygons, doing many things, and perhaps polygon classes are involved, or other selection rules (named polygons, polygons by region or layer, etc.). Hm, one fairly probable use-case would be, say you want thermal relief on mid layers, but not on the surface: the
OnMid polys can be excluded from such a rule as the second object.