My best guess is that when you are edting the loss amounts for the default perm, you have invalid json syntax, causing the plugin to load up the default config in memory (most plugins work that way). One simple test you can do is, using the default config, revoke all restoreupondeath perms from all groups and users, then grant the restoreupondeath.admin perm, then verify all items are restored. If that works, then conclusively you are editing the config wrong, or you have assigned multiple permissions leading to the plugin picking the wrong amount for you.