Mine works this way.
1. I press the R-key.
2. I HOLD the ALT-key and press + on the Number Pad. I press it 1, 2, or 3, etc. Make note of how many times you press it.
3. To get back to normal speed, I press R-key, and then HOLD ALT-key and - on the Number Pad.
4. The ALT-key on the right does not work on mine. Nothing happens whenever I press ALT-key on the right. So, I use the ALT-key on the left.
5. It works for me on a Logitech MX Wireless keyboard.