To accommodate situations where a TB member quits mid-term and is replaced by the next-highest vote-getter in the previous election.

Here's how I put it in another thread that may be more clear:

- In most instances makes someone who has served two consecutive terms (4 years) on the TB take at least a year off before running again.

- In the instance of a replacement TB member, allows him or her to be elected 2 times after the appointment if he or she is appointed after the first year of the term of the person he or she is replacing. If he or she serves over one year of the term of the person he or she is replacing, he or she may only run one more time after serving out the over-one-year term before taking at least a year off.

I think this achieves those goals in a simple, straightforward way.