well, it depends how the communication works.
If it works by sending thoughts, then there shouldn't be anything to stop you sending a number one. If it relies on sending memories or feelings, there might be more trouble.
Have you ever had a dream where you were reading a book or a computer screen? I had one last night. I was trying to type a website URL onto the screen and I kept screwing it up. For whatever reason, the part of my brain that usually handled the comprehension of written words and stringing them together in coherent form wasn't working right. However, I got a very clear sense of where I was, what I felt about the people around me and so forth. It was just reading and writing that were beyond me.
It could be that this communication ability connects to feelings or images rather than to developed higher-brain concepts like words and numbers.