Confusion about accelerometers

Wikipedia first paragraph on accelerometers:

[...] an accelerometer at rest on the surface of the Earth will measure an acceleration due to Earth's gravity, straight upwards3 of g ≈ 9.81 m/s2. By contrast, accelerometers in free fall (falling toward the center of the Earth at a rate of about 9.81 m/s2) will measure zero.

https://en.m.wikipedia.org/wiki/Accelerometer