In a campaign in which I play, our DM is using 'taint' rules. Seeking to protect myself against taint, I found about taint absorbing items. The SRD has this to say about them:
Some natural substances absorb taint and thus protect those who are exposed to carry them. Examples include a pure jade rod the size of a human finger, a sheet of vellum prepared from a year-old lamb, an intricately carved piece of lightning-struck oak, or a silk sash. The GM can create other examples appropriate to the campaign as well. Regardless of the shape or substance of the item, taint-absorbing items cost 100 gp each.
As an item absorbs taint, it darkens, softens, and gradually rots away over seven days. During that time, it absorbs all taint to which the carrier is exposed. Possessing multiple taint-absorbing items at the same time can protect a character for longer than seven days, but the benefit does not accumulate indefinitely, as shown on Table: Taint-Absorbing Items.
As the text says, the benefit does not accumulate indefinitely. Nor does it stack perfectly. The table shows that two taint-absorbing items protect someone not for 14 days, but for 12. The longest protection is given when one carries 4 items with them, resulting in a protection lasting 16 days. After that, more taint-absorbing items create a shorter and shorter protection, with 5 items lasting 15 days, 6 lasting 12- And 7 or more items will last you even shorter than 1 item would: Only one day.
Am I misinterpreting this table? Is it actually an acumulative effect, as in "One item absorbs for seven days, a second item adds 12 to that" etc.?
Or, if not, what would be a possible in-universe explanation for this?