Since picture #2 is a blank page, that implies you are including the correct number of blank pages. If so, then you are still missing one blank page at the end as picture #27. That's because picture #1 is actually a composite of both the front and back covers which reduced your actual picture count by one picture. So, the correct number of total pages in the doujinshi is 28 as issued by the author.

Base +8

한국꺼는 왜 맨날 별점테러 당하지? 일본애들이 그러나....ㅋㅋ

Base +3