This is mostly correct, but there are other factors that affect the payout. In my post The Ultimate Guide To Steemit Payouts, I wrote the following:

Why does my future payout keep changing?

Upvotes will increase your payout and flags will decrease your payout. If you haven't received any new upvotes or flags, there are several other reasons why your payout may have changed:

There is a fixed amount of new STEEM created each week to be dispersed to users as rewards in a rolling 7 day period. At any given time, the system is making an estimate of how much you will be paid based on what percentage of Steem Power-adjusted votes your post possesses.

Let's pretend a piece of content is currently worth $5. But then, many other posts suddenly become highly-upvoted. The money to pay those popular posts needs to come from somewhere, so a portion of your post's value is reallocated to these newly-popular posts. Now your post may only be worth $4.50.

Another reason your payout may change is price movements in the 3.5-day moving average of STEEM. If the price of STEEM increases, the value of your post will increase, all else equal.

edited: messed up my link