Why is SUM function throwing #multivalue error ?

Hi,

I have a peculiar issue. I have a column which indicates the total number of hours [Hours 1]  a ticket has been in "Do not consider for SLA" state.

I want to sum up the column and display it in a different table.

When I select the column and apply the SUM function through the tool bar, it works fine.

However, when I directly apply the SUM([Hours 1]) formula, I am getting a #Multivalue error. Am I missing something ? Has this been discussed earlier ? Any pointers in this regard will be highly useful.

Am also attaching a screenshot for reference.

Cheers,

Somu.

P.S Am using WEBI XI version 12.3.0