Ra being called?

[Plenum]

Or can it be related to the callers level of evolution and understanding, which then determines who responds...

yes, I tend to go with that interpretation as well.  I first heard it suggested by Scott Mandelker, in one of the talks that he put up on youtube.

If there are about 350 thousand souls (back in the early 80's) who were calling 'at that level'; they would be conscious adepts working at indigo-ray level, which has a 'consonance' with Ra's density of origin.  Many of the themes of 'indigo ray' (6th chakra), like the seeking of unity, overlap with the lessons of 6th density.

If that analogy holds true, then the numbers calling the Confederation (630 million), as a percentage of the Earth's population at that time (4500 million), then gives about 14% seeking at green ray positive and above.  Which is a reasonable estimate for potential positive Harvest.  14% is a fair number.  Not huge, but also a little slightly disappointing.  But it's a fair number.