How to fill empty field values to 0 in Splunk ?

[nilbak1]

I have data in below format in Splunk
where I extracted this as Brand,Files,Size.

Now at some places, where size is showing empty, I want to replace them with 0.

I have used | fillnull value 0.
| eval Size=if(isnull(Size), "0", Size)

But still values are showing empty.

I have used below query

index=*** host=*** source=****
| rex field=_raw max_match=0 "(?[a-z]+),(?\w+\-?\d?.*)\,(?\d?.*)"
| table Brand,Size,Files
| eval _counter = mvrange(0,mvcount(Brand))
| stats list(*) as * by _counter
| foreach * [ eval <> = mvindex('<>' , _counter)]
| xyseries Brand Files Size
| transpose 0 header_field=Brand column_name=Files | fillnull value=0

and the result i m getting as like below

After using | fillnull value 0,
I am getting 0 for those files which are not there for 2nd,3rd,4th brands.
But not where size is showing empty.

Can anyone help me with this ?