Gran's box

Driving home at night, you notice that all the lights in your house/apartment are on. As you park the car, they all turn off at the same time. The house is empty and the doors are locked from the inside. You check your watch. The big hand is on the 4, the little hand is on the 1. You'll be late for work. At work, you find an email in your inbox. The sender is yourself. Puzzled, you open the e-mail you apparently sent to yourself. Inside is the message 'the out for watch watch.' You look at your watch. The little hand is on the 4, the big hand is on the 1. You look back at the screen. The fourth and first words have swapped places. 'watch out for the watch.' You look at your watch again. Your watch is digital.