Sound comes out of my headphones or speakers incorrectly.

There are three things to consider: settings, operation and connection.
Please check each in the following order:

1) Confirm the settings on the Serato DJ Pro screen
1.　Check if [Error: Failed to connect audio!!] or [Driver Not Installed] message shows at the bottom of the screen.
If it is shown, read the DDJ-REV7 FAQ > [Troubleshooting > "The message [Error: Failed to connect audio!!] is shown, or the virtual deck disappears immediately on the Serato DJ Pro screen."]
2. Click the icon in [My Serato] on the upper right of the screen.
3. Check that the [Serato DJ Pro is activated] and [DDJ-REV7] are shown on the screen.
If not, read the DDJ-REV7 FAQ >[Troubleshooting > "The Serato DJ Pro screen does not react anything when the DDJ-REV7 is connected."]
2) Check the volume level operation
1. Play a track.
2. Set the TRIM knob to the center (12 o’clock).
3. Slide the channel fader to the top.
4. Slide the crossfader to the center.
5. Turn the MASTER LEVEL knob to 2 o'clock.
If the MASTER LEVEL indicator lights up more than half way, there’s no problem in the settings and operation.
If you don’t hear any sound from the headphones at this point, check the following:
6. Turn the HEADPHONES MIX knob to the center.
7. Turn the HEADPHONES LEVEL knob all the way to the left.
8. Press the MASTER CUE button.
9. Turn the HEADPHONES LEVEL knob slowly to the right.

3) Check the connection of speakers and headphones
For details, refer to [Basic operation] and [Example of connections] in in the Quick Start Guide.
Even if you’ve already connected them, disconnect and reconnect them to make sure they’re properly connected.
*You can't output audio from PC/Mac speakers.

You can read the Quick Start Guide [here].