Evaluating Hall Effect Sensor - Practical Explanation of Bops / Brps?
Yes, these values show the sensitivity of your sensor. The B is your magnetic flux density strength (in Gauss) and Bop is your operating point, and Brp is your release point. By the + and - values, I would think this has something to do with it sensing from their North and South poles. 

Let's use the AH3781 as an example. Essentially, it looks like when the South pole reaches 25G, the sensor will switch on and go low (due to the internal pullup note, it is safe to assume that the output of this sensor is HIGH), then to switch it back OFF again, you will need 25G sensed on the North pole. 

Confirmation

In fact, if you look at this DATASHEET, you will see I was correct. The important thing to note, is the smaller the number is, the more sensitive your sensor is.

Also, be aware of the direction of magnetic flux. Different sensors will detect on different axis. The datasheet will usually tell you, then you can figure out the best orientation for your sensor or magnet.