A Duv value provides information on the distance and direction of a color shift from the Planckian locus on the CIE 1960 u-v coordinates. When Duv value is closer to zero, the light source is more like an ideal one .
Distance of the illuminant from the Planckian locus on CIE 1960.
(+ Duv. – Duv. Symbol: With + sign for above and – sign for below the Planckian locus.)
It looks like there is CCT difference between left and right side.
In fact, only a little differences.
They are in the same CCT, but in different sides.