Thanks for getting me a little closer, my owners manual doesn’t have anything about “Set speed warning light” after concentrating around page 209 and the “get to know your instrument cluster” section. Nothing about that little number in a circle on any of the 718 pages.
Welcome to the forum. If you put your van info (year, trim, gas/hybrid, etc.) in the signature line of the UserCP it will show up at the bottom of each post and might help someone with a similar van answer your question.
The User's manuals may have different pages for different years and models of the Pacifica. You might also want to check the specific owner's manual for your UConnect system for better instructions.
Maybe as a part of Keysense, it looks like the maximum vehicle speed in 2018s can be set in the UConnect settings and then a number such as 65, 70, 75, etc can be chosen. See about page 566 in the multimedia section of the main owner's manual for a 2018. You might have to try changing the setting to see if the number changes or goes away.
If you don't have a 2018, try looking for the "multimedia" section at the front of the owner's manual and look through it until you find information about UConnect settings which might be displayed in a chart. The index of the manual isn't as useful as you might hope.
My van doesn't have that option but has an option for the Navigation to alert me if I go over the speed limit (which is posted in the Navigation maps) by a certain amount. The setting for speed warning can be found in the settings for Navigation in the touchscreen which is probably different that what you are seeing.
Let us know if you get it figured out.