@Ganjaaa It says right in the beginnigng of the script:
tiers, attr = {}, {}
tiers['rare'] = {
color = 66, -- color of 'RARE' text
extra = {0, 0},
attrNames = true, -- show attribute names instead of rare
chance = {
[1] = 20000,
[2] = 5000 -- chance for 2nd stat...