Locke tells her that Jack diagnosed a four-week period of healing, but Rose says "you and I both know it's not going to take that long". This is in reference to the airport flashback, revealing that Rose knows Locke was in a wheelchair before the plane crash.
Locke shares with her that Jack predicted a four-week recovery period, but Rose counters, "we both know it won't take that long". This exchange alludes to the airport flashback, which reveals that Rose is aware of Locke's past disability as a wheelchair user prior to the plane crash.