All scores thrown on the same course layout in multiple rounds will be used to determine the SSA and ratings for that layout except when wind is significantly different
So it looks like the SSA is still being calculated from the first round, which would be the 49 (1000 rated.) It looks like each throw is then worth 10 ratings points.
The second round gets a little tricky. Because there wasn't a Scratch Score, and the general low scores of the field, we see compressed ratings. For instance, a 51 in the second round rated higer
(4 points) than a 50 in the first round.
I'm not sure what formula they apply to appease the "except when the wind is significantly different" scenario in the above PDGA statement. But I reckon these ratings will be recalculated before everything is said and done.