In the interest of full disclosure: I put the same comment as above on the Cocky Turtle Facebook page and received this reply:

The Cocky Turtle
Hello Jim, we apologize for this and are aware of the situation. We have made adjustments in the POS system, as a Tito’s mix is supposed to be $9 instead of $10. We have the drink menu set up that way to include the rates for customers who would like a double shot or upgrade of the type of alcohol used. However, I will agree with you that a note should be added about the mixers add-on- that will be corrected and reprinted promptly. You will notice during your trip, that our drink/ cocktail prices are on the cheaper end of local pricing. Please return with your partner for a round of drinks on the house.

My reply to them:
Jim Haughton
Thanks for the quick reply and offer of a free round. When I ordered, I asked for the drink tall but with just a regular (single) shot as I don't like strong drinks. Maybe this was the confusion.