Update item for Number field is not working

I am trying updating the current list column (Item Quantity field). I am using update list item. If the both IDs match, return quantity. However, getting this error: Coercion Failed: Unable to transform the input lookup data into the requested type.

The values are not empty. But if I use lookup column, it retrieves the value. However, I have to use the workflow.

Kindly assist.