I've checked: "Use my conversion tracking data and bids to optimize for conversions".
I have 3 conversion types, but one of these is not relevant in terms of the optimization.
How do I get AdWords to focus on one or two relevant conversion(s)?
There are two types of conversions:
Conversions (1-per-click)
Conversions (many-per-click)
You can select the one that is most useful for you by going to Tools and Analysis > Conversions > Settings > Edit Settings
If you would like to delete one or more conversions go to Tools and Analysis > Conversions and then click on the green spot next to the check box of the conversion you want to delete and select "Deleted"
You can also add new conversions by going to Tools and Analysis > Conversions > +Conversion
Here are some links that could be interesting for you: