Hello,
The OVA/OVF is a tar archive of all the VM files. By default it compresses the files including the VMDK. Furthermore, the VMDK size compressed in the OVF/OVA is calculated only based on the used space and not the whole space.
In your case, since the used capacity of your first disk is 77 GB and second disk is 740 GB, these two numbers are again compressed to fit into the OVA/OVF format.
However, if you are still in doubt, you can try to import the OVA/OVF into your environment and check. If found any issues, I suggest you to use ovftool.exe which is a utility specially developed for exporting/importing OVA/OVF.
Below link for your reference to ovftool usage:
https://vdc-download.vmware.com/vmwb-repository/dcr-public/bb505ca7-88b5-4b11-aff4-f59125ab27bc/f3d0...
Thanks!