In order to advertise the addresses from a Meraki client VPN to the non-Meraki devices, go to Security Appliance > Configure > Site to Site VPN, and then under VPN Settings and then Local Networks, you'll see the IP range there(Currently the range is set to 192.168.55.0/24) and then set Use VPN to "Yes".
my issue with the whole thing is how disjointed things are to simply create a vpn tunnel. I have general complaints about the process with Meraki. sometimes it is an improvement to do things differently than others, but in the case of VPN, which is built on a standard, its weird and frustrating that the various pieces necessary for building a tunnel are in different places. Its not built using a straight-foward workflow for the various steps required.
Also a complaint, since I'm already ranting: when I created the non-meraki tunnel I added two Meraki sites. this visually appears to be one tunnel with two network ranges. but that's not what's happening under the hood. Its actually building two separate tunnels from each device. That took a lot of time to figure out...and its silly.