Simple Sum of float columns with null values - but using less complex formula?

[jerome]

Hi
Is it normal that in order to process a simple sum of float type columns that contains sometimes null values,I am forced to use such a complex formula (see below in yellow)? Or am I doing something wrong here?
Not using the IsNull formula, or even just not using the parentheses in my formula, lead to a wrongly calculated sum column….
Many thanks for your help.

 

[Support]

You can use a simpler expression: see the example in the attachment.