Initialize apps with a viewlist

Hello Community,
I'm creating an app which have to store the value of the Item Number as picture attached. And when i added the blocks as picture black line frame in order to keep on counting the Number to "07" intead of from "01" when everytime open the app. And it seemed ok when doing in computer. But when I installed it to mobile and open it, it didn't work and showed error as picture. As i know the system can't get the value because of empty list when first initialize, but i don't know how to set the blocks.
I deeply appreciate who can help me solve this problem!

You are setting value of BBB in last and getting value in start so you are getting error
set your code like this
when screen1 initialize then store value tag = BBB value = your value

That is not the issue here. As OP said,

OP, replace the highlighted blocks in your image with:

Thank You very much, and i will try it.

Thanks for your solution, I had tried it on mobile, the result is empty when i pressed button.

Hi there, sorry, I can't get your mean as when initiate first time, it's a empty list, no value to store. For my example, when i get Number to "6", i store the value, then i refresh and initiate again, i aslo have to take the value "6" first in order to get "7", otherwise, i only can take "1" from beginning. Do you mind expaining more detail about your solution, thanks!

Make sure to use the not equals block (≠), since that's what I've used here.