The website says "on Saturday except the first week of August, Thanksgiving week, the first and last weeks of the year" but this does not match the pattern for 2007 or 2008
In the Jul-Dec there are 26 issues
In the Jan-Jun there are 25 issues (no issue for the first week of January)
Since the irregularity on the first # 26 does not skip a week, this would be set up as to roll over on issue 25. The 26th issue in the second half of the year would have to be received as a supplemental.
The irregularity check will complain that 52 issues were expected, but 25 entered. The current irregularity check can only check that the first position of the numbering pattern matches the expected issue count of the periodicity. But we do need to trigger the rollover on the volume, so we need to define the last two weeks of the year as irregularities. So we receive 50 issues the first 50 weeks, then one supplemental issue in week 51, which we have to define the enumeration for, then the next predicted issue will be the following year's first week.