Symptomatic hypo is when they are low and they are not acting normal. They might seem disoriented, have trouble walking, lethargic, etc. Most of the time when our cats hit lime greens they are extra hungry, but other than that they will seem just fine. If they go really low though, they'll start acting funny. And what counts as "really low" can vary some from one cat to the next. In general, I would say anything in the 30's (low 2's on your meter) or lower you want to take a little stronger action to bring them up (high carb food). 40's are really still pretty safe, but you don't want to ignore them - a snack (low carb food) and further monitoring is definitely in order.
In general, if the lime green happens near the nadir, giving regular low-carb food is all they need to start rising since the insulin should be starting to wear off anyway. If it happens early in the cycle, they still have several active hours of insulin left so that's when they might need higher carb food. I tend to think of honey or karo as a last resort - generally only if the kitty isn't able to eat themselves, or if you don't have any high carb food in the cupboard. If they can eat higher carb food on their own, they don't really need us stuffing them with short-acting sugar.
I think a reduction tonight is a good idea. And again, don't worry if the PS number is high tonight. Go with the reduction anyway.