Your Ability Score Bonus is determined by every 2 stat(istic) points
above the number 10. Thus, at 12 you receive a +1 bonus. Odd numbers
above 10 are rounded back to the previous even numbers when determining
the bonus. If you have 15 STR(ength), you get the same bonus as if you
had 14 Strength.
The numbers 10 and 11 give no bonus and will reflect a bonus of +0.
If a statistic is 9 or below, your bonus becomes a penalty. Every addit-
ional 2 points below 9 decreases your bonus more. Thus, if you had a
Strength score of 7, your 'Ability Score Bonus' would reflect a -2 for
Strength. When calculating penalties, you round upwards to the nearest
odd number. If you have a statistic at 8, the penalty is the same as if
you'd had a 9.
Please know that when considering statistics, just because two numbers
may give the same Ability Score Bonus, they are not equal. For example,
two characters are given a ring of Wisdom (+1). The first character has
16 Wisdom and the second has 17 Wisdom. Naturally, they both receive a
+3 Ability Score Bonus, however when they both wear the ring only the
second character advances to a +4 Ability Score Bonus for Wisdom.
* When calculating the Ability Score Bonus, the current
score is used (the left of the two numbers for each statistic). In the
example above, if both characters removed their rings of Wisdom (+1),
then both of their Ability Score Bonus scores would return to +3.