The reason you may see a discrepancy in the Ad Extension data in Optmyzr reports when compared to the AdWords interface is because when AdWords reports data for Extensions, it is not just for that specific Extension.
The clicks that you see by default against the extension are for any click that happened on the ad when the extension showed. This is the case with other metrics as well. The data you see in the reporting widget in Optmyzr is for that specific extension. It is possible to see this data in AdWords by selecting the segment 'This Extension vs. Other'. That will show you how many clicks that extension actually got and how many clicks other extensions got when this extension showed. In AdWords you can segment the data and the numbers you see for 'This Extension' should match what you see in the Optmyzr widget. The reason we show data in this manner is because the numbers you see in AdWords under the default setting can be misleading. You'll also notice that the totals in AdWords will not match when the individual numbers are added up.The screenshot below is for Sitelinks but will apply to all extensions.
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