How do you measure the "dose" and add it to the tank?

The bottle I saw at the dealer looked like you'd just invert it in the tank spout and hope to get close.

My son has mouth wash that you squeeze the bottle and 1oz goes up to the top of the bottle in a little chamber, and then that can be poured out. That seems simple to me.

Or maybe there should be a "Yamalube" injector, like my old Yamaha 2-stroke motorcycle. Mixing oil and gas wasn't hard but the auto-injector was nice.

Am I overthinking this?