The AP-ANT-17 is a 3x3 AP which matches the AP-11x capabilities. As such, as Seth mentioned, it does not matter which antenna leads you connect to the AP connectors -- so long as you connect all three. Not connecting all three would cause performance loss.
The only time you would need to worry about which connectors to use is if you are using a 3x3 antenna connecting to a 2x2 AP. One lead of the antenna is left disconnected and this will vary from antenna to antenna.
Generally, when mounting the antenna to the wall the pigtails drop straight down. There may also be "weep holes" for condensation drainage at the bottom of the antenna. The weep holes should point down.