The formula you're thinking of is Ohm's Law. It allows you to calculate values when as many as 2 variables are present.
The key to the table is as follows:
E = ELECTROMOTIVE FORCE = VOLTS
I = CURRENT = AMPERES
R = RESISTANCE = OHMS
P = POWER = WATTS
So, known values in this case are: 12V, and 110W load (one bulb?) So solve for I.
According to the table, (P/E) = I
If you only calculate (110W/12V), you get just over 9A.
Consider all other loads on the vehicle at once, stereo, heater fan, other lights, etc. You'll come up with more than you think.
Either way, you might as well get the biggest amperage alternator you can stuff in there.
Hope this helps,