You're working with both Outlook (desktop) and Outlook on the Web (browser) and therefore want to use the same default signature in both clients.
If your Outlook on the web (OWA) email signature is incomplete, you have reached the character limit for OWA.
With Exchange Server on premises, Microsoft enforced a 8KB character limit in OWA email signature settings.
We have not yet seen limitations with Exchange Server online (Office 365).
If you see incomplete email signature in OWA when using the the Xink platform, please reach out to us and we'll help check your image size and resolution acc. to our Best Practices.