Is the 10-15 mins extra ab workout benefiting me?

Demmuscles

I do a workout in the morning, today was 30 mins of level 3 30 Day Shred, plus I pause just before cool down and do some extra planks, crunches, reverse crunches for a few mins. Then in the arvo I walk the dog for 20 mins, and once my kids are in bed at night I do 10-15 mins of crunches, planks, push ups etc and some chest work with dumb bells. I am just wondering, seeing as I do the last bit on its own with no cardio etc, will it actually be doing anything for me? Thanks.