String to Numeric Changing Field Values?

[ScottWW]

I am working with a dataset from a CSV file. Perhaps the fact that it is a CSV and not a XLSX is the answer to my question, though I am still curious as to why this is happening. 

I attached two screenshots so everyone can see what's happening: The Field "Base Market Val" is a string, but I need to convert it to numeric to run formulas with the values. After the Select Tool is used to change from V_String to Double, the values in the field changes. 

Can someone please explain why this is happening?

[JosephSerpis · Accepted solution]

Hi @ScottWW the issue is your field has commas if you remove them then convert to a numeric field then the values won't change. 

[ScottWW]

Makes sense, I figured it was something simple like that. Thanks!