There are special symbols you may include in the fixed endorse string that the scanner will vary per-item basis:

Symbol	Usage
<TIME>	the current time
<MDY>	the current date (MDY)
<YMD>	the current date (YMD)
<DMY>	the current date (DMY)
<U>	up arrow
<D>	down arrow
<L>	left arrow
<R>	right arrow
<C>	page count
<C#>	page count with N (#) digits

If you run the "Ranger Image Display Test" app, you can see these demonstrated in the endorsement section.