Though I don't really use it myself, it has been suggested (by someone who apparently tracked it, sorry I can't give proper credit because I don't recall a name) that you can predict ratings somewhat by taking the S2 line, subtracting the S1 line, then multiplying that number by 2.5 and adding it to the S1 line.
So, for this guy, his S1 vs RH was 49. His S2 vs RH (starting line) was 54, so a 5-point difference. Multiply it by 2.5, (round up to) 13. 13 + 49 = 62.
Not saying it's right or wrong, but that's how it has been explained in the forums before and some people swear by it.