Sure you do!
You have a Librem 5 with PureOS, which is Debian-based a.k.a. awesome. You can do whatever you want. 
# Get the source code
apt-get source gnome-power-manager
cd gnome-power-manager-3.32.0/
# Install build dependencies
sudo apt-get build-dep .
# Make the changes you want using your favorive text editor
vi src/gpm-statistics.c
# Build deb files
dpkg-buildpackage -us -uc -b
cd ..
# Install deb files
sudo dpkg --install gnome-power-manager*.deb
# Enjoy running your modified gnome-power-statistics program!
gnome-power-statistics
The above is basically the same procedure as in Tweaking difficulty level of Chess to make it easier, via minor source code change