The AMR sensor sensitivity varies by individual AMR sensor.
The Hon and Hoff in the datasheet indicate the specific range for that product.
(The product standards for the MRMS501A-001 are Hon of 2.5mT minimum and Hoff of 0.5mT maximum. Some sensors are Hon = 1.8mT and Hoff = 1.6mT. Other sensors are Hon = 1.1mT, Hoff = 0.8mT, or are Hon = 2.2mT, Hoff = 2.1mT. In this way, sensors with random sensitivity are wrapped in a reel.)