The circulation run time, is the maximum amount of time you will allow the system to circulate for if the circulation delay time is exceeded. i.e. This is how long the system will run for if it has been idle to long.
As before we start from the default screen, which will be similar to one of the images below. You may note that the middle image has the system running in automatic with both boost and circulate on.

Press the info key (key 7). You are now in the main menu, and the screen will be the same as the image below.

Press the down arrow key (key 6) five times. Please note, the up and down arrow keys can be used to scroll through all the menu options.
The screen will now be the same as the image below.

Press the right arrow key (key 5). If this is the first time you have set this parameter, the screen will be the same as the image below. If this is not the first time you have used this setting, then there may be a number displayed rather than all zero's as below.
This uses the 24 hour clock format. i.e. hh:mm:ss.

When you have entered the hours, press the enter key (key 8), and the cursor will be moved to the minutes entry, and so on until you have entered the seconds. Pressing the enter key after this will return you to the main menu, where you can press the left arrow key (key 3) to be returned to the default screen, or the up or down arrow keys to scroll to the next menu item.