SPA 128, both positive and negative values, tend to vary from one to the listed max. This is not reflected in descriptions for items or abilities related to them. In many cases it doesn't even make sense that it works that way. Funeral Pyre states it reduces the duration of a DoT by 50%, but seems to reduce it by up to 50%, with a minimum of a 1 tick reduction. Mortiferous Wounds, Cytotoxic Wounds, and other DoTs of the 1:36 duration should demonstrate this fairly clearly when cast with no ear focus or other buff focus, showing a 50% maximum reduction to 48s, and a minimum reduction of only 6s to 1:30. Pyre of Jorobb, Pyre of the Shadewarden and other 30s duration DoTs will show 18s to 24;s, coming just up to half or losing only 1 tick. This can also be demonstrated positively with the standard ear focus of detrimental duration, and a long term debuff such as the Malo line of spells for mages and shamans. Cast it on something, note the duration in the debuff window. Continue, and it will jump around to a large number of different values. A group focus is 26%, and Malosinata is 20:30 in base duration, so this will easily show variations of entire minutes.
SPA 128 has been this way since at least 2007 (maybe since always). I don't really like that it works this way either. If you have an ext detrimental focus and Funeral Pyre buff on, you can look in the spell display window to see the focused duration min/max.
