Problem, total sum listpicker, please help
It looks like you don’t know the difference between a list and a list picker.
Also, you need to read more on lists and lists of lists.
Your error message came from the marked parts of
Please read the How to Work With Lists article in the Lists section of FAQ
https://sites.google.com/view/ai2-faq-view/home
Also readhttp://www.appinventor.org/bookChapters/chapter19.pdf
Your List Picker blocks suggest that you should be keeping a two column table
(list of lists) with names in position 1 and numbers in position 2 of each row.
Also, your for each block should be for each row in that table,
where you should take item 2 of that row (its number) and add it to the sum.