There are definitely more symbols then there are letters in the alphabet. So that could mean he has multiple ciphers or that some symbols are substitutes for words, possibly common phrases.
Though I was advocating this as a possibility, I should point out that he might include some actual punctuation in the cipher as well as the standard 26 characters, so it's still possible that it's just a substitution cipher.
Additionally, it's possible that some of these characters aren't characters at all, but common repetitions. I'm thinking particularly of those slashes and backslashes.
Additionally, it's possible that some of these characters aren't characters at all, but common repetitions. I'm thinking particularly of those slashes and backslashes.