Convert Custom Dimensionon field from string to Number #UiPath Insights #GoogleLooker

[Emilotto9]

Hi all, 
i’m new on the community and  I’ m a newcomer to Looker technology. I am trying to add a new Custom Dimension Field which should serve me as a numerical class to be able to do sums. 

In particular I describe the scenario: 

I extract from this string : 
"64 dpps found for NZL" that is a result of a log message , the value 64 

this value appears to me as a string even though I format it as a Number when creating the custom dimension. 

The expression I use is as follows: 

substring(${robotlogs.message}, 0, position(${robotlogs.message}," ")-1) 

The purpose is to read it as a number and be able to do sums by creation date. 

Could someone please direct me ? 

Thanks in advance.
Emilotto9.