"Show me where you live. I can find you there." He knows the brain doesn't do well with numbers and letters in a dream state, so Hyun-su wouldn't be able to write down an address or a phone number to Jae to take away. And Jae's bad with numbers so he wouldn't be able to memorize them if Hyun-su recites the information. "Can you do that?" It's his dream, he should be able to do that much.