Can someone familiar with this organization please explain how they can legally pay you 80 hrs per paycheck when your assigned & worked duty hitch is 7, 12 hr. days (84 hrs). 

you are salary. look at your offer letter and divide the pay by 26 pay periods. they divide that amount by 80 to get your hourly rate for when you go over 12. they divide the amount you get per pay period to get your daily rate for an extra shift. why they don't just divide the pay period rate by 84, I don't know but the pay is the same either way.

Sure. On your 7 day hitch, payroll pays your first six shifts as 11.5 hours (accounting for a 30 minute "lunch break" I guess) and the seventh shift is 11 hours (not sure why they short us another half hour on that one except to equal 80 so they've told me, which yeah seems wrong). In theory then, we should be doing like what CVS pharmacies now do across the country--closing for 30 minutes, while we take that lunch break (insert eye roll). They did change the workover thing lay least so anything over your normal 12 is OT, which didn't used to be that way. 
Side note: Know this 11.5/11 hour payroll thing also applies to when you put in for PTO/EML. You should only be taking 11.5 per shift or if you are taking the last day of your hitch off you only need to submit for 11 hours of PTO. Or if taking a partial day, a portion of 11.5 not 12. Payroll should catch it if a pilot puts in for 12 hours, and only actually charge you 11.5, but not necessarily. I helped a guy get back almost 15 hours a few years ago because his previous supervisor had been sending through all his requests overcharging him each time. They can do a correction and give you back if that's the case FYI 

It may be true about the 11.5 hour thing but you are not being shorted as your pay will match up to the full amount of your salary, either your offer amount or the amount on the pay compensation schedule. Also, no lead or anyone else puts in PTO for you at PHI. You do it yourself on the bonus voucher. I call BS on that reply as well.

If you read it I said they allot for a lunch break. Almost every regular job does that and corporate follows suit in accounting. That's directly from payroll lips. And you can put in for PTO all day long as much as you want but payroll does nothing with it until and unless your supervisor approves it. That supervisor also has the ability to adjust it before final approval. Payroll sees it but won't process it until supervisor approves. I spent years in the role there so you can keep your BS.

At PHI, if you do nothing in the payroll system you get what's in your offer letter.  Clocking in and out daily is for the FAA duty time, not looked at, touched, referenced in any way by payroll.

To get overtime or time off, you submit something and payroll does see that.  That's where the math is to the pilots' advantage.  Your overtime is time and half of one eigthieth of your pay, not one eightyfourth.  So you get a little more. 

Likewise, vacation is docked at less than 12 hours a day, even though everyone knows thats what you're going to miss.

So at PHI, work your schedule and you get exactly what you're offered without submitting anything to anyone.  (Had a guy that quit, HR forgot to drop him, and he kept getting paid even though he didn't show up. )

If you work overtime you get paid a smidge more than time and half.  If you take time off, you get charged less than twelve a day.

That time and a half is taken by dividing your pay by 84, not 80.