Potassium

One caution: MFP may understate how much potassium you're getting. That's because it wasn't required to be listed on US nutrition labels until 2020-21, and many food database entries on MFP pre-date that. Most database items are crowd-sourced - entered by average MFP users - and when potassium wasn't on the label, they didn't have a source to enter it from.

When I've been concerned about whether I was getting enough of some nutrient that might be undercounted here (or uncounted), I usually do one of two things:

• Pick a couple of typical eating days from my diary, and spot check them using a reliable source like the USDA FoodData Central Database.
• Do a web search for "foods high in (that nutrient)", click on ones from reliable sources, then see whether my routine eating habits had a reasonable amount of those foods.

If you're asking for where the MFP recommended amounts came from, that's also usually based on US food labels' daily values for each nutrient. Specifics about those are here:

https://www.fda.gov/food/nutrition-facts-label/daily-value-nutrition-and-supplement-facts-labels

If you want to learn about risks when getting too little or too much of a given nutrient, I've found the US NIH's factsheets on each nutrient helpful. These are usually available in both "for professionals" and "for consumers" versions. I prefer the "professionals" ones because they tend to have more in-depth information, but I haven't found them to be too technical. Here are both for potassium:

https://ods.od.nih.gov/factsheets/Potassium-HealthProfessional/ - for professionals

https://ods.od.nih.gov/factsheets/Potassium-Consumer/ - for consumers