Okay, great.
But just think about it from it's theoretical perspective. It's all about revenue recognition. Specifically, the timing of it.
Is revenue earned only when a long-term project is completed? Or is it earned over the course of the contract?
For GAAP purposes, the answer is: revenue is earned over the course of the contract. And the best way to gauge how much revenue is earned is...what percentage of total estimated cost has actually been incurred. The matching principle at work, right?
If you have a construction contract and you estimate that the cost of the job will be $1,000,000...if you have $500,000 into the job, then you are 50% complete, right?
And if you bid the job out at $1,400,000 to the customer....then you are able to recognize 50% of that contract price. Or $700,000.
But what about what you have billed the customer in progress billings? Remember
BILLINGS DO NOT EQUAL REVENUE. Say that over and over to yourself, if you need to, as it is a common mistake I'd see with baby staff people in public accounting.
In our example, we are able to recognize $700,000 in revenue. But what if we have billed the customer $800,000 so far? Well, we 'owe' them goods and services related to $100,000 worth of our to-date billings, right? So you have an overbilling (liability on the Balance Sheet) of $100,000. And typically, that $100,000 must be moved out of revenue (where it was credited when it was billed) to a liability account.
DR - Revenue $100,0000.
CR - Overbillings on Long-term Construction Contracts $100,000.
But what if you have only billed them $600,000? Well, in that case, you have earned $100,000 more in revenue than you have billed for...so you have an underbilling - an asset on the balance sheet. Think of this as sort of an unbilled receivable.
DR - Underbillings on Long-term Construction Contracts $100,000
CR - Revenue $100,000.
If you grind that theoretical basis into your brain, running the numbers makes alot more sense.
There are a few little nuances in there that you'll learn about once you get into actual practice in the real world (like what happens when you run over budget, for example, on costs...which fouls up your percentage complete late in the game by giving you crazy percentages of 110% complete or something, if you are not paying attention and forget to change your estimates)...but for your purposes now...that's it in a nutshell.
I find that the best way to approach accounting is not to memorize a bunch of rules...but instead, to understand the
theory behind it. Then it just becomes about the application of that theory to various situations. Which is why the FASB exists! The Financial Accounting Standards Board is all about application of theory.
By the way, completed contract is rarely used except for tax purposes. Up to a certain point, construction companies are allowed to use it for tax purposes...which of course, defers the payment of the taxes until the end of a job...which makes them very happy. But once certain revenue thresholds are met, a construction company must convert to percentage of completion, even for tax purposes. Bummer for 'em.
And it's never GAAP in audited financial statements.
Upps, didn't know this thread was supposed to be DS9 free, I just read a bit through the last few pages of it, and since I never watched Roswell, that post was one of the few I actually had something to say about. 
Can he help you?