Here is a quick, hard summary of the (sMeba) mewa you can use in your arcane calculations. As seen herein, there are nine mewa, each consisting of a numeral and color combination. Thus, we do not merely speak of "1," but of "White 1." (Made the White 1 a little larger to emphasize the point.)
Each of the mewa has certain characteristics, as defined by various and sundry texts. Thus, you can employ the mewa to determine the nature of a day, a past life, a future life, and so on. To go into all of the possibilities here would quickly become boring, so I will just stick with the most important point, which is the associated element. Our first mewa, White 1, is associated with the element Metal. It is called the "Mirror of Medicine."
Black 2 (sometimes Blue 2) is associated with the element Water. It is called the "Mirror of Demons."