Pointed out the window[1]: 1/2000th
The interior of my office[2]: 1/30th
My office feels brightly lit to me, but the ambient light level is only about 1-2% of what it is outdoors. I estimate that 0.25% is roughly how bright it is indoors on an overcast day or outdoors at twilight on a clear day. It's dim, but people with unimpaired vision have no trouble seeing in that light level and the planet would still look spectacular.
1. Grass and trees with no sky in frame.
2. Shades open, light grey walls mostly. Same ISO and aperture.