If you're comparing the data you see on Data Studio vs App Store Connect and notice that there are discrepancies, don't worry. This misunderstanding can be clarified by:
Breaking down your Units by using the ProductTypeIdentifier dimension: you're be able to differentiate app downloads from updates, re-downloads and sales when you use it.
Realizing that the data you see from the connector comes directly from Apple's official API itself which is published on PST (Pacific Standard Time - Los Angeles / Vancouver)
1 - The ProductType identifier field
To get a complete view of this dimension, please visit Apple's official documentation.
Here's our short summary of the main filters you might want to use:
If you want to see app installs only
ProductTypeIdentifier starts with 1
If you want to see all your in-app purchase sales
ProductTypeIdentifier starts with IA
If you want to see in-app subscription sales only
ProductTypeIdentifier starts with 1A9
If you want to see in-app auto-renewable subscription sales only
ProductTypeIdentifier starts with IAY
If you want to see updates only
ProductTypeIdentifier starts with 7
If you want to see
ProductTypeIdentifier starts with 3
2 - Confirming timezone discrepancies
To confirm that any other discrepancies are caused by timezone differences you can do the following:
Go to the Trends menu
Select Units on the left-side menu
Change timezone to PST (drop-down menu on the right side of the date picker)
It should look like this:
By doing this you can change the timezone to match what you see on the connector.
What else can go wrong?
Whenever I'm still finding major and inconsistent discrepancies despite the above I ask myself the following:
Am I comparing the data from the right apps?
Are you using any other filter on your Data Studio dashboard?
Am I comparing the exact same dates from both?
Am I comparing the right metric (ex: Units vs Sales)?
Given that the data you see on Google Data Studio comes directly from Apple's Official API there shouldn't be any doubt that what you see on your dashboard is the source of truth of your app's data.
Speaking from personal experience, it did take me a few weeks to completely understand all the nuances on Apple's data. After doing some digging I realized I have much more control on the data I see by fully exploring the ProductType Identifier dimension.
Still, if you're still struggling with this, do send us a message so we can help :)