Normalize audio 3dB lower than expected?

So I have a sample that peaks at -10db, I normalize it with a setting of -10db expecting -10db back but I get -13db.
If I normalise anything to 0db it renders to -3db.
Event volume at 0db, no fades, no effects or channel settings.
Using Cubase 9.0.1
Anyone know what’s happening?

-3db pan law is happening.

Please don’t ask me to explain any further though…it confuses the hell out of me :laughing:

what are you using to measure the loudness,some loudness plugins read 3db less than others don`t ask me why,but is explained somewhere on da web ,if you are using Voxengo span to read the loudness set the metering switch to DBFS+3db.

Ah your right! It’s a mono sample. When I pan hard left or right it does peak at -10 db as expected, but panned to the centre it peaks at -13db. That’s weird.
Thanks for the help!