Expand allows a mage to increase something in size, quantity, etc.. A common reason to Expand spell energies is to create an area of effect for an explosive spell. The mage would first Create a fireball, then Project it, and finally Expand it.
Contract allows you to lessen something in size, quantity, etc.. A mage may use this spell effect in order to counter another mage’s spell. For example, if an enemy mage creates a fireball and hurls it at the party, a mage who can Contract Fire and who has enough spell points built up already may attempt to cast in time to reduce the enemy fireball down to nothing.
Energy point cost is based on the amount of the expansion. To expand something in size, it costs 5 points of energy for every square foot you want it to increase. Spending less than that would reduce the size increase or decrease to 3/4 of a foot, 1/2 of a foot, 1/4 of a foot, and one square inch. Increasing the point cost would add a foot per point. Add one point per turn the increase or decrease is to last.
If the increase or decrease is for something nonphysical, the GM will have to come up with a sensible point cost. For example, to contract 20 points out of an enemy's AGL, it would cost 20 points plus one point per round the effect should last.