This is different for everyone but for most it is either a half syringe or a full syringe of lip filler, usually the full syringe. Your Denver injector or Boulder injector will be able to advise the best amount of filler for you based on your natural lip goals and overall aesthetic balance of your features.
It can also depend on what 'canvas' we're starting out with. Most of the time, we do the treatment in 1 session. But, for example, if we're starting out with very thin lips, we may divide the dermal filler treatment into at least 2 sessions giving the lips time to slowly build which leads to a MUCH more natural look. Also, if you already have larger lips or if your lips are very dehydrated/wrinkled, you may even need two or more syringes which is done over two or more sessions (usually 1+ months apart) to get the result you're wanting. Patience, grasshopper.