You need 2000 Light on your weapon to finish soul attunement. The first picture was with the value of light set at 1999. It is obviously not enough.
I'll update these values as I figure out more but so far:
Feeble: 1 Light
Gentle: 4 Light
Brilliant: ?
Blinding: 8 Light
Newborn Star: ?
Tiers:
'No Activity': 0 - 199
'Indisctinct Activity': 200-399
'Faint Activity': 400-599
'Slight Activity': 600-799
'Modest Activity': 800-999
'Distinct Activity': 1000-1199
'Robust Activity': 1200-1399
'Vigorous Activity': 1400-1599
'Intense Activity': 1600-1799
'Extreme Activity': 1800-1999
'Bursting Activity': 2000+ (Complete)