The measurement delta E is basically how close is what's being displayed to what it's supposed to be.
A delta E of 5 is good, but these come pre-calibrated with a delta-E (∆E) < 2 which is super accurate. Each monitor is literally shipped with a calibration report just to give you the insurance that these have been through some serious quality control and I love that!
I don't see a need to upgrade anytime soon, and it checks off all the requirements for what I need in a monitor. Awesome!