Checked Zopp to have all the facts.
The 27 from that Futures drops a few weeks from now. Zopp drops Wimbledon qualifications from last year which was and still is 16 points from a last round loss.
What he gained now is 35 points for qualification and losing in the first round on Wimbledon (25 + 10), and 10 points for the challenger.
The 35 is mandatory in the rankings, and the 10 enters only if big enough. Both of them enter into Zopp's rankings and they knock out the IW 8 points qualification (because there's one extra tournament since last year).
That's 565 - 16 - 8 + 35 + 10 = 541 + 45 = 586.
There is usually no mistake in the calculation (all the ATP ranking rules are implemented in the algorithm correctly and checked for 6 months now - although bugs may still exist but they're very rare).
The mistakes will almost always be in the placement of the tournaments (the exact week they drop off). The OP contains a link to the full rankings xls file which can be expanded and everyone of you can see where all last year's tournaments are placed. You can thus do the calculations yourselves and point out mistakes if the points are not calculated correctly because a tournament is not dropped in the correct week. You can see there the Best 18 score and predict which tournaments get cut off because of new tournaments. This was the case with Nalbandian which had his 65 Davis Cup points placed in the QF instead of SF. This is not the case with Zopp, which (until proven wrong by official rankings) I say has the correct value in my table.
P.S.: Where did you get 19 ? Oh, you meant 35 - 16... But you missed the IW 8 point drop because of one extra tournament.