Bad arguments when selecting from a ListView

I have an app with a ListView, when i select one item, i am receiving the following error:

Bad arguments to -
The operation - cannot accept the arguments:

End Application.
My app displays all the rows from the TinyDB, but when i try to select one of them, i receive this message.
Here are the blocks. In the Designer screen, i only have:
A Button.
A ListView.

That's all.

selected is a string, not number, you can not minus a string by 1.

Each of your Elements is a string of the form tag:v1:v2, right?

To get the three parts,
set templist to split Selection at ':'
set tag to select item 1 from templist
...v1 .... 2
...v2 ... 3

Hi Kevinkun.
Thank you for your quick reply.
I am learning MIT App Inventor and just bought a book, "App Inventor Databases and files".
The author is Edward Mitchell.
At some part of the book i saw an example where the App is reading a TinyDB and i try to adapt it to my app. This is where i copy that segment. And in it, is substracting 1 to Selected. I think this is a bug. I will try the option that ABG is suggesting.
Thank's anyway.

P.S. I like YAML format for compound Element values.

Informative and easy to parse.