Lumens ?

[Monster762]

I have a 4x4 room currently running t5s with veg and bloom bulbs staggered with a 600w led centered between the 2 fixtures. Lumens at canopy read just under 28000 evenly across room. Is that enough for flower. This is my first indoor grow. Flipped switches 2 days ago. If I need to add (or move closer) I want to do it now. Lights sit 4 to 4-1/2 ft off canopy. This is my UFO. Almost covers whole space. It's a bit brighter than this pic makes it look.

 

[Monster762]

ok so how do I know then. And why do plant lights go by lumen output?

 

[Homesteader]

Lumens and Lumens per watt are measures that have value (with selecting LED emitters and COBs in particular) but as a grower you need to understand PAR and phytochrome signalling to accompany it. Emitters and COBs will cost more as lumen output increases in most cases.
A high PAR value doesn't necessarily give you any better quality light. A green LED would be next to useless by itself.