LTFT and STFT

First of all Im new to tuning. I was datalogging a 2009 silverado with a 5.3L engine. I was looking at the LTFT and the STFT just to get familiar with the HP Tuners software. The truck has a cold air intake and to my knowledge never been tuned. I noticed the STFT were about +/- 3%. What has got me confused is the LTFT were -10.0% the whole time. I thought that the negative number means the ecu is pulling fuel from the engine is that correct? If so then why would it not be adding fuel due to better air flow?

the MAF has never been rescaled in the tune? Put a stock airbox in and see how the trims change. I mean you're probably ok as is, but basically once you change the intake out the ECU can't measure airflow as accurately without being retuned.

Ok, thank you. I was thinking that is what was taking place but wasnt sure.