There are a few reasons why you might not be reaching out to the expected number of contacts:
Your global sending volume settings are limiting. Adjust them here.
Note that there is a "starting volume", "warm-up rate", and "max volume", with the definition of each located on the page itself.
You have too many campaigns running with follow-ups
GrowthGenius prioritizes follow-up messages before reaching out to brand new contacts
So, if you have a global sending limit of 100 emails per day it's quite easy to reach that limit just due to follow-ups that are being sent across your campaigns.
To resolve this, add more time between follow-up messages in your campaign (this provides more days of no follow-up activity to allow new contacts to be reached out to)
Your campaign sending volume setting is set too low.
Solution: Go to Campaigns, click on the campaign you want to edit, click settings in the top right corner, and adjust the sending volume.