Dear Mark
you said that you are maintained relative limits in customization . I observed that in your table Relative Limits are not tracking for the threshold value 3. (Pl refer my screen shot)
Alerts will be triggered based on these relative limits . these can be maintained in 2 ways , in first .. we can maintain this at substance level of class SAP_EHS_1026_001 , characteristic SAP_EHS_1026_001_REL_LIMIT.
During running of substance data fill programme in to SVT table , system initially check at class in the property tree level, incase no data found it will take from customization.
Even if we see your tracking log.. it showing that threshold value 1 instead of 3.
Balajee