20 is a good value to use. Motion Phase is a timeline which controls the birth and death of the combustion. 0 is default, but as it cycles through it dies out at later values. Whilst it phases the pattern changes, the faster it's animated the more furious the pattern cycles. Essentially phase is like a seed, a mathematical algorythm. You need to animate this value adjusting, or use the explosion feature metioned just a bit further down the page.
Drift conrols how quickly or slowly the fire animats in the Z axis.
Meaning it will rise quickly or slowly upward. Explosion , enablng explosion adjusts the phase values for you allowing it to apear and explode like a proper explosion. This option is necessary to make a propper explosion rather than the fire being there ever continuously going. Smoke is the third colour in the colour boxes, if enabled when the explosion begins to die out it fades into black and then fades out completely. If you click on set up explosion it will pop up a box which has start and end times for combstion, allowing you to specify when the explosion starts and finishes.