瑜伽論記 6.84

6.84

依五處，二十相者，初三處各三相，第四處有五種，第五處有五，合前為十九。又復發起堅固精進下，合於五處總為一相，并前二十也。

Regarding the twenty aspects based on the five bases: the first three bases have three aspects each; the fourth base has five kinds; the fifth base has five; these together make nineteen. From "furthermore, giving rise to firm vigor" onward, combining the five bases makes one general aspect, which together with the previous makes twenty.