For a number of reasons, reports on human consumption of oxygen produced by trees vary. Here are some other quotes which may be more or less conservative than in my report:
"A single mature tree can absorb carbon dioxide at a rate of 48 lbs./year and release enough oxygen back into the atmosphere to support 2 human beings." - McAliney, Mike. Arguments for Land Conservation: Documentation and Information Sources for Land Resources Protection, Trust for Public Land, Sacramento, CA, December, 1993
"On average, one tree produces nearly 260 pounds of oxygen each year. Two mature trees can provide enough oxygen for a family of four." - Canada's environmental agency, Environment Canada
"Mean net annual oxygen production (after accounting for decomposition) per hectare of trees (100% tree canopy) offsets oxygen consumption of 19 people per year (eight people per acre of tree cover), but ranges from nine people per hectare of canopy cover (four people/ac cover) in Minneapolis, Minnesota, to 28 people/ha cover (12 people/ac cover) in Calgary, Alberta." - U.S. Forest Service and International Society of Arboriculture joint publication
Several of these sources suggest that it all depends on the tree species and their local populations. Other things that will increase oxygen availability to humans is a tree's health and where you live when computing tree oxygen availability per capita.