Eg. On Monday, if I have only 5 chapters in the stockpile, you will only have access to 17 chapters instead of 19 since 2 chapters will be released to the public. At the end of the week however, the amount of chapters you have access to will always be 19.
Note: There will be more than 5 chapters in the stockpile at all times so this is a relatively stable tier. During holiday seasons however, this may change.