The number that is multiplied by the square of the rolling time in seconds is related to the rolling distance from the last cushion until the ball stops. For a table 100 feet long but with normal cloth, you would expect about a 25 second lag time if the ball stops just before the cushion and the multiplying factor would be something like 1/6 instead of 2 since the lag is 12 times longer than a "normal" lag.
On the other hand, if your lag only comes back 60 inches (on any table) and it does it in 6.0 seconds, the multiplying factor is about 3.333 (due to the short length) and the nominal speed of the table would be 6*6*3.333 = 120.
The speed of the cloth has nothing to do with the length of the table. It is only related to how fast the rolling ball slows down. The different factors quoted for different lengths of table just save you from having to do the math like in the 60-inch lag -- the lag length is built in to the factor.
