Stupid ILL18 question

Really stupid question and I'm embarrassed but...

In Don's BJA3, pg 62, he lists the Illustrious 18 indexes. I understand the indexes are the departure points from BS. Easy example is the 16 vs 10. BS says hit, index says stand if the TC is >=0. The index in this case is inclusive for counts of 0 and above.

What about 12 vs 5? BS says stand, but does the index is -2. My first impression was to view it like the 16 vs 10 index so that it would be "stand on 12 vs 5 at TC -2 or greater". However, I'm beginning to think this may not be correct. So is the 12 vs 5 index to be viewed as"

Stand on 12 vs 5 at TC of -2 or greater (more positive) or
Hit 12 vs 5 at TC of -2 or less (more negative)?