Thanks for your message!
This leftover you are talking about, contains the same amounts of ingredients as the rest of the shake.
So don't worry about missing a big percentage of proteins. These won't drop any more than the other ingredients.
If you prefer a 100% liquid shake you could add some extra water, or when your shake is almost finished, add some water to this leftover and shake again!
Hopefully it's clear to you now, and enjoy our shakes!