String/text TO number(int/float) - not working "correctly"?

this is obviously me not understanding what I need to do to satisfy the backend - im sure its obvious.
when I encounter this stuff, I usually do a clunky workaround, but I feel like id like to know the "right way" finally.
(edit: also returns anomalous/unreliable results with non-decimal integers - so if you imagine all this all without decimals, causes same issue - although sometimes, for some numbers it works)

in short, this code snip doesnt work correctly. were taking a value, like 12.5:1 in text/string form, dropping the ":1" of 12.5:1 part, attempting to move the 12.5 into a pre-defined real/float declared variable, add 0.1 to that (making it 12.6), and finally sending it along.

the rest works, but the math part is where the issue lies (doesnt produce "the number" + 0.1) - what dumb thing am I doing here?

How do you know which block is working, which one is not working?
Try to show the variable on one or two labels, before and after you try to change its value.

use Do it to debug your blocks, see also tip 4 here App Inventor: How to Learn | Pura Vida Apps
see also Live Development, Testing, and Debugging Tools

Trying to push the limits! Snippets, Tutorials and Extensions from Pura Vida Apps by icon24 Taifun.

From my phone...

Set global inputParts to split input at ':'

Set global output to select item 1 from inputParts

If length of list inputParts > 1 then
Set output to output + 0.1*(select item 2 from inputParts)

i know its part of converting the string to a number and then trying to do math with it.
its a common issue I encounter on app inventor and I usually just do an ugly workaround - in script this is fairly easy to overcome, but here I have struggled

we have seen your block clearly, now show us the result of variable BEFORE and After your try to change it, on 2 labels.

that would help a lot - thanks for the heads up, didnt realize that existed.
now mine is greyed out on everything when i right click - is there something more I need to do to enable this function?

Did you start your Companion on your phone?

Did you ask AI2 to Connect->Companion?

Did you scan or retype the displayed code into the running Companion to connect it to your app?