The most common reasons for discrepancies between Opteo conversion data and Google Ads conversion data are either the date range you're viewing, or the conversion actions being considered.

For the date range, you want to make sure you have the exact same date range selected in Google Ads and Opteo. E.g. if you're making a report for June in Opteo, select the 1st of June - 30th of June in Google Ads.

For the conversion actions, you want to make sure that the conversion actions you have selected in your Opteo report settings (under the Recipient Profile section) are the same conversion actions that are included in the Google Ads dashboard.

Here is where you would check which conversion actions are included in the Opteo report: