above / over
Two prepositions of place, amount, and rank.
Above and over overlap, and either will often do. Prefer above for a position higher than something else with space between, and for rank or a figure on a scale: above the clouds, above average, the office above mine. Prefer over for covering, crossing, authority, or motion across: a blanket over the child, a bridge over the river, over the limit, power over the committee.
Examples
Use The range hood is mounted 30 inches above the cooktop.
Use Fog settled over the valley.
Use Temperatures rose above ninety.
Use She has authority over the budget.
Over is the usual choice with numbers in the sense “more than” (over two hundred pages). Above remains natural with average, zero, and similar benchmarks.