When you create or edit a data source in Google Data Studio, you get the option to select the data type of the data source field. 

One of the data types supported by Google Data Studio is ‘numeric’: 

There are three numeric data types in Google Data Studio:

1. Number – select this data type, if you want Data Studio to expect a number (includes floating-point number) when processing the field in the specified data set.
2. Percent – select this data type, if you want Data Studio to expect percentage data when processing the field in the specified data set.
3. Duration – select this data type, if you want Data Studio to expect time duration in seconds when processing the field in the specified data set. 

For example, consider the following data set:

• The field ‘Number of orders’ is of type ‘Number’. 
• The field ‘Percentage of Sales’ is of type ‘percent’. 
• The field ‘Duration’ is of type ‘duration’.

If we connect this data set to our data source then when deciding the data source schema (structure):

• we should set the data type of the field ‘Number of orders’ to ‘Numbers’.
• we should set the data type of the field ‘Percentage of Sales’ to ‘Percent’.
• we should set the data type of the field ‘Phone Call Duration’ to ‘Duration’.

Now if we create a report from this data source then it would look like the one below:

This report matches with our data set:

The only difference here is that the values of the ‘phone call duration’ field are displayed in a different format. For example, Data Studio displayed 230 seconds as 00:03:50

If you convert 230 seconds into minutes, it would be 230/60 = 3.83 minutes or 3 minutes 50 Seconds

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Using incorrect numeric data types

Consider the following data set:

• The field ‘Number of orders’ is of type ‘Number’. 
• The field ‘Percentage of Sales’ is of type ‘percent’. 
• The field ‘Duration’ is of type ‘duration’.

If we connect this data set to our data source then when deciding the data source schema (structure):

• we should set the data type of the field ‘Number of orders’ to ‘Numbers’.
• we should set the data type of the field ‘Percentage of Sales’ to ‘Percent’.
• we should set the data type of the field ‘Phone Call Duration’ to ‘Duration’.

But what if, when deciding the data source schema (structure):

• we set the data type of the field ‘Number of orders’ to ‘Duration’.
• we set the data type of the field ‘Percentage of Sales’ to ‘Number’.
• we should set the data type of the field ‘Phone Call Duration’ to ‘Percent’.

Then that’s how our report would look like:

Data Studio will automatically convert all the values of the:

• ‘Number of Orders’ field to ‘Duration’ data type
• ‘Percentage of Sales’ field to ‘Number’ data type
• ‘Phone Call Duration’ field to ‘Percent’ data type.

So when you select an incorrect numeric data type while defining the data source schema, you get incorrect/un-expected data in your reports.