Note: There is an easy way to remember the base height. Take the number of groups and multiply by 3/4. Then discard the fractional part. If you have more than ten groups, add a bonus height for each group after ten. It's also important to remember that this is the base, or minimum height. If you want to know the base height for a 13 group strike (and don't have the table handy), take 13 * 3/4 = 9.75. Ignoring the fractional part gives you 9 to start with. Then, we have more than 10 groups, so the bonus applies and we add 3 for a total of 12 base height.