has next to no mention of anything like "delta system update". The first link is to this page. There does seem to be a sourceforge package called delta update, but that is not a debian specific tool. It also seems to be really old, the newest version is from 2005. I think you'll want to go back and get the name right. I've been using Debian for years, and I've never heard of anything like "delta system update". There are thousands and thousands of packages in the Debian repositories, and I don't claim to know more than a small portion of the available software, but since nobody has written a response to you, I'm betting you have the name wrong.
Here's the link to the google results -