Custom Item Error?

I can't do this anymore lol. I'm trying to make a custom item, but every time I want to give myself the item, it just says 'Unknown Type'. I will show the screenshots below and also an error I sometimes get. Also, can someone explain the type thing in the first row of the code that's beside the Object ID? I don't know the pattern as to which how it is followed. I only know that it is a hex value that is unique.


