I did the same calculation myself earlier today and came up with 2*24 + 17*30 = 558
Whether we use 2 or 3s for the guessing time is something to debate. However, the all-zeros guess time is something to compare a personal performance against.
Note that an experienced planner shouldn't over-do Zeroes on either PreO or TempO (in my opinion) and you must come to some sort of balance between difficulty of the stations and overall number of Zs.
yup ... just looked at the WTOC maps ... eeek!

