Update description2.md

description2.md

@@ -17,7 +17,7 @@ The key of achieving zero bubble is to breaking a backward pass into a B pass an
 
 | Comparison assuming T_F=T_B=T_W                                                      | 1F1B    | ZB1P     | ZB2P | ZBV (Recommended) |
 | ----------------------------------------------------- | ------- | -------- | ---- | --- |
-| Bubble Rate                                           | (p-1)/m | (p-1)/3m | 0    | 0   |
+| Bubble Rate                                           | (p-1)/(m+p-1) | (p-1)/3(m+p-1) | 0    | 0   |
 | Activation Memory <br> (Compared to 1F1B)             | 1x       | 1x        | 2x    | 1x   |
 | Pipeline Communication Volume <br> (Compared to 1F1B) | 1x       | 1x        | 1x    | 2x   |