I'm not sure I understand the question. The offline bundle contains a Java 8 JRE, Java 8 is not recommended for XP as far as I am aware. On XP best would be to install a Java 7 JRE from Oracle and use the normal REW Windows installer.
The naming is probably a bit misleading. The offline installer has everything it needs to install and run REW including a Java runtime. The regular installer will look for an existing Java installation, if there isn't one it will direct you to download one, which requires an internet connection. REW itself does not need an internet connection to run, whichever installer you use.