Mutate filter not working

Hello All ,

I am trying to display one SQL column value TIME_DIFF in Kibana. which is shown below.

But it is displaying in Kibana as shown below .
image

I am trying to convert this using mutate ,

> filter {
> mutate { convert => ["TIME_DIFF", "float"] }
> }

Kindly help.

Thanks and regards
Saravana S