Pretty new here and still learning and testing the tool but here is my suggestion:
Bind Label A value to a pageVar ālabelAā so that value 21 be stored into that var.
Bind label B to another pageVar ālabelBā, and set its value as a formula with something like pageVar.labelA*0.33

where ā5ā is a number I picked as an example. In your case, it should be the number you want to round.

But looks like you first need to get acquainted with how formula works. Do you know Excel formula? You should apply the same principles here.

Also, do not use an input field for displaying the result of your math formula. Thatās why you have an āinversibleā error message. Simply use a text component for such display purpose.

Thanks Fred, I changed the input field to a text component, but I still cannot make the formula work,

The formula is applied to a text field and the idea is that it looks at what is in the input field above assigned to var A and first calculate 40% of it and than make sure it rounds the number down to 0.5

When I type the formula like you did I get this error

Thanks Bravo, but this will also round to numbers like 5.6 and 5.7 etcā¦
The idea is that the numbers I will use are weights, and the smallest weight I have is 0.5kg
so if the calculation says I need to use a weight of 6.74kg the round formula needs to show 6.5kg,
if the calculation was 6.76kg than the rounding needs to go to 7kg

I hope it makes sense, I donāt know if this is even possible.