Few things . Extract usually is darker unless you add at the end of the boil. Beer in your fermenter will appear to be darker . 4 liters shy of water will make it a little darker since your not diluting the full amount.
SRM (color) isn't measured in the fermenter during active fermentation. Wait until it is in the glass before making a final judgement.
Color in the fermenter tends to be darker than beer in the glass. I've noticed that perceived color can change during active fermentation.
As @Jag75 mentioned, color also tends to be darker with concentrated wort (19L vs 23L). (FWIW, product information sheets for Briess Golden Light DME show a color of 4 @ OG 30 and 7 @ OG 60).
Does anyone have "typical" numbers for how much lighter extract-based beers are when using late additions?
@pokerloict, what was your water source (tap, R/O)?