If I'm not mistaken you have three different things you can do there. A "p", ","(comma), or a "w".
P and comma perform the same thing, they perform a pause. With that, you can do for instanc,e your voicemail password "phone#,1234".
A "W" in the command performs a wait, so if you commonly dial into the same prompt system, like a dial in phone directory at someone's office. If you know the first thing it asks is english or spanish you would insert a pause to select 1 for english, then if you always go into the directory which is 3 you would place another pause, but then each time you are wanting to enter an extension to reach someone different, this is where the wait comes in. The wait, does just that waits for you to enter a number. So time for an example.
We will say 1(555)-555-5555 is the directory switch board number.
We want 1 for English
We want to then go 3 for the directory. (4 second pause between questions)
We then want to goto extension #1234
15555555555,1,,3w
It dials goes through the english prompt automatically, then when it says, "Please dial the extension for the person you wish to speak with", the phone will wait, you dial in extension #1234 and your off!
So basically now with that set, you hit the speed dial, wait for it to pause enter 1234 and you're there.