“Type of things” is the format of your list. So, for example, if you were running on a list of users:
Type of things: User
List to run on: Search for Users
Or, if you were running on a list of numbers coming from an API result…
Type of things: number
List to run on: Result of previous step’s task’s each item’s result’s item’s price
Again, these are just examples. The type of things is the format. The list to run on has to be a list of values that matches that format. The format can be API specific, so it doesn’t need to be a generic text, number, date, etc. I don’t know enough about the architecture of the API you’re using, but you’ll need to locate the format that matches that list you have (currently in red).
Sometimes, Bubble will show a little message to help you auto-select the right type. If you see that pop up when you change the list expression, try selecting Bubble’s suggestion. Also, it’s possible that the list you have now (in red) isn’t the one you actually need. It’s the one I’d start with based on your other screenshots to find the best pathway to all those other values.
So, I’d keep the list you have and change the type to a selection that matches your list (which you’ll know is correct once the expression turns blue).