The low threshold example uses a 0x0A value, which corresponds to 10 in decimal, so 10*6 = 60 uT is the low threshold limit the example have set, but it doesn't specify whether it's a positive or a negative limit, or for which axis the limit is.
/*! low threshold limit */
uint8_t low_threshold;
/*! high threshold limit */
uint8_t high_threshold;
Also, both low and high threshold limit are uint8_t, so I would like to know if it's possible to use a negative limit in order to get a interrupt, since both the raw and compensated micro tesla values of the magnetometer are sometimes negative.