Differences in being paid for Rabbit-Hole Jobs

[Seabody]

One day I was planning to improve my sims' house.
I checked his pay, figured out how many hours he worked per day, then made an estimation on the price of the renovation.
I worked out that it would take him x days to earn the required funds to pay for the renovation.

He worked, and during each day, he did not get a promotion or a raise.
But when it came time to renovation, he did not have the money to pay for it!
I repeated this test with another sim.
Here was my logic:

Lets assume he earns §100 per hour, and works a ten hour day.
100 x 10 = 1000.
But when he got paid, he was only paid §956, for example.
Since when has 100 x 10 = §956???

Is this a bug, or is it a feature?
To recap, I'm asking about not earning what you should earn.

[gerrr00]

In my experiences it depends on when you get to work.  It goes by how long you are there.  If I am in need of extra money, I always have them show up to work before I get the carpool notice, then as soon as I get the notice, off to work they go.  On high free will I have had my Sims, adults and children, skip work/school.  That could effect the amount of money made.  I have never sat and paid complete attention to if they get the correct amount owed to them or not.

[Seabody]

After hearing about sims leaving work early, I always make sure that they're there on time. And I think that this was a single sim too.

[TheChronicR]

It's definitely because of being a bit late for work. And do you really care about fifty dollars if your Sim gets thousand a day?

[Phyre]

It's definitely because of being a bit late for work. And do you really care about fifty dollars if your Sim gets thousand a day?

There's a saying here in Holland that roughly translates to:

"Who doesn't appreciate the little is not worthy of the big."

And like already mentioned, the descrepancy most likely results from missing some minutes of work at the beginning or the end.