A 4:30 marathon is 10:18 per mile, or 6:24 per kilometer, for 26.2 miles. In kilometers it comes to almost exactly 32:00 per 5K: an even pace reaches 10K in 1:03:59, 20K in 2:07:59 and 30K in 3:11:58, each within two seconds of a multiple of 32:00, which makes the plan easy to carry in your head on a course marked in kilometers.
Like most goal times, 4:30 does not come out to a whole number of seconds per mile. The exact pace is 10:17.9, which charts round to 10:18, and 10:18 held for the full distance finishes in 4:30:03. To break 4:30 you need 10:17 per mile (4:29:37) or faster; 10:13 per mile finishes in 4:27:52. Per kilometer it is the same: 6:24 per km finishes in 4:30:03, and 6:23 per km in 4:29:21.
Half an hour over 26.2 miles is about 1:09 per mile. That is the gap between this goal and a 4 hour marathon at 9:09 per mile, and between this goal and a 5 hour marathon at 11:27.
The tables list the clock time at every marker for an even pace and for a 2% negative split. The negative split starts at 10:24 per mile and passes halfway in 2:16:22, 1:22 behind the even plan, then runs 10:12 per mile. It is still 38 seconds behind at mile 20 (3:26:36 against 3:25:58) and makes the time up over the last 6.2 miles.
Riegel's formula, which the race predictor uses, puts a 4:30:00 marathon level with a 2:09:30 half marathon and a 58:42 10K. It is a prediction for a runner trained for the marathon distance, so use it to sanity-check the goal against a recent race, not to set it.