No, the multiplier makes the engine larger.
Jump Drive Efficiency:
Divide the size of the ship you want to jump by the Jump Drive Effiiency and you have the size of your standard, run off the mill jumpdrive.
This jump drive can (with a squadron jump) take a total of three ships (the jumpship itself plus two other ships of equal or smaller size) through a jump point and will arrive at a random point within a radius of 50,000km around the jump point on the other side.
Now, if you want to take two additional ships with you, for a total of 5, you have to use (Max Jump Squadron Size-5 (size x 1.2) and your jumpdrive will be 20% larger.
If you want to appear further away from the jump point, in order to avoid a beam base parked on the jump point, for example, you can go for Max Squadron Jump Rdius 250k (size x 1.1), so your jumpship and company will appear at a random spot in a radius of 250,000 km around the jump point, again increasing the size of your jumpdrive by 10%.