The Speed Factor Chart on page 315 has a formula at the bottom of it:

(Let's make it a bit simple, and call RunMP + JumpMP/2 = FV (for Final Value))

1+ ((FV-5)/10)^1.2 (for speeds above 25)

However, the chart itself is generated with the formula:

(1 + (FV-5)/10)^1.2

Note the position of the first left parentheses. In fact, both the MUL and MegaMek uses the second formula. Take the example of the Locust LCT-6M (MUL page 50, it's Walk 14 with a MASC) The first formula gives a Speed Factor of 3.72, the second formula gives a Speed Factor of 4.19 (which the MegaMek breakdown shows) Leading to a BV of 956 (again, MUL agrees with MegaMek, although the MUL does not provide a breakdown.)

So 2 questions

1) Is the movement of the parentheses deliberate or an oversight?

2) If it's deliberate, then the MUL provided BV of the LCT-6M is incorrect, right? It should be 884?

Also, are you sure? The following are the Speed Factors for higher speeds (attained by VTOLs and Hovers, or units with MASC and/or Supercharger)

24 3.59 (chart, also works with the second formula)

25 3.75 (chart, second formula actually gives 3.74, but close enough.)

26 3.44 (first formula, second formula would be 3.89)

27 3.58 (first formula, second formula would be 4.04)

28 3.72 (first formula, second formula would be 4.19)

29 3.86 (first formula, second formula would be 4.34)

In other words, the LCT-6M is better off (BV wise, at least) being a 12 speed with a MASC and 1 jumpjet (and leaving the excess weight empty), than a 14 speed with MASC.