I said "What time should we revise" he said "Don't know. When are you free"
Please discuss.
It simply means that he's not sure about his own schedule so he's asking when you'd be free to revise. When you give him a time....he'll check to see if he's available for that time according to his schedule.
Do you like this guy? If so, then you would need stronger signals to determine whether or not he's interested. The example that you have provided is unfortunately not even a signal. It's simply a polite question regarding time schedule.