*I* use a bit more, 1cup/cf (7.5 gallons), added to my mix. This translates to 2Tbl/gallon of mix.
Since it has "some" lime in there, perhaps a bit less. But if the pH was 5.9, it couldn't have been much of a charge ...........
It's hard to overdo lime, but easily under applied (5.9 pH)...