Maybe 30 to 40 degrees comfort? Looking at specs of the EE Apex quilt (which uses the same insulation) you could maybe argue for 20 degrees based on weights and assuming insulation thicknesses. Kifaru isn't very good about posting detailed specifications so it's tough to estimate.
I have used mine down into high 30s low 40s. Didn’t do anything special, just wrapped myself up good. If I slipped out of the blanket I would wake up because I was cold and have to reposition