The source's espresso-martini variation combines vodka, coffee liqueur, syrup and chilled espresso in a shaker with ice. Coffee liqueur contributes sweetness as well as flavor, so changing brands can change the drink even when the volume stays the same.
The retained quantities include half an ounce of coffee liqueur and one ounce of espresso, but not every component measurement. That makes the available text an incomplete formula rather than an exact recipe to scale. The source also permits cold-brew concentrate as a different coffee base.
Chilling the coffee before shaking can help keep the dilution more predictable. Record the full quantities from a complete recipe and adjust sweetness deliberately instead of adding syrup automatically. Coffee does not remove alcohol's effects, and an alcohol-free drink needs a separately balanced formulation rather than a claim that the espresso counteracts the spirit.
The conversation
A good question can make a better brew.