In the diagram below, you can see how the hydrofoil functions on both tacks.
On the Port tack, the floatation of the ama counteracts the heeling force from the sail. In very strong winds, the sailor can supplement the ama’s floatation by adjusting the foil to add lift in an upward direction.
On the Starboard tack, the sailor adjusts the angle of attack of the foil to cause it to pull downward, counteracting the heeling force of the sail.