Yes. One of the things to do to help treat a venous ulcer is to put your feet above your heart as often as possible. For example, you can lie down with your feet propped up on pillows.
Above your heart is a specific instruction, and it is not the same as up on a footstool. Lying down is the example because that is what makes the height possible.
The reason comes from the cause. A venous ulcer forms because of high pressure in the veins of the lower leg: the one-way valves that keep blood moving toward the heart become weak, or the veins become scarred and blocked, and blood flows backward and pools in the legs. The increase in pressure and buildup of fluid makes it harder for nutrients and oxygen to reach the tissues. Elevation goes along with compression stockings worn every day, walking or exercising every day, and taking medicines as directed.
There’s no set time or number of times beyond “as often as possible.” If you have been given a figure by the person treating you, that figure came from someone who could examine the leg.
It’s also worth knowing that elevation isn’t treated this way for every leg wound. With ischemic ulcers, the wounds also called arterial ulcers, raising the leg can turn it pale and cool to touch, and there may be aching pain in the foot or leg that goes away when the leg is dangled down. Those are symptoms of that wound, not advice for or against raising the leg. If raising your leg makes the pain worse, that is a finding worth reporting rather than something to push through.