Cartridge Output Voltage and it Affect on a Turntable with Pre-amp/USB Outputs

I purchased a Pro-ject Debut III / USB turntable some time ago ( what was I thinking) and I wanted to upgrade the turntable so I purchased a new Ortofon 2M Red cartridge. After I put it on the turntable, I noticed some clipping indication through the USB port on my computer. I don't hear the clipping (or I don't think I do) but I would like the output at about 80% to 90% of 0db. The turntable has no attenuation/gain control.

The question I have is the stock cartridge has an output of 4mV and the replacement cartridge has an output of 5.5mV. Is the higher output of the 2M Red causing the clipping? Should I look for a replacement cartridge that has a 4mV or less output (as long as its sufficient output for the turntable's pre-amp)? Or do I get an Audio Interface and adjust the attenuation/gain with that device? 

I'll await the feedback... 
Hard to tell. there are no specs posted for the overload voltage for the internal phono pre-amp.  How do you have it connected to the rest of your system?  USB out to a computer/DAC or are you plugging it in to a receiver or integrated amp or a pre-amp.  If one of the latter 3, are you plugging it into a line level or aux input?  It should not be plugged in to a phono input. 
Thanks for answering.

I have it connected pre-amp level (with RCA) out of the Turntable to a line level input to my integrated amp. My amp doesn’t have a phone input. The USB is connected directly to my Mac.