The scales won't shut off as long as the weight is changing, so you could be adding concentrate for 5 minutes, but as long as the weight is changing it won't shut off. Once you put one ingredient in, then you hit 'Tare' to reset then add the next.
If the weight stays the same, that's when the 60 second timer starts. All you have to do is make sure you have all ingredients to hand before starting,then hit the 'Tare' after each one has been added, you'll have no problems.