My suggestion is to try to familiarize yourself with Non-Structrual Carbohydrates (NSCs), starch, sugar, and how they all pertain to a horse's diet.
See the asterisk on this page where Nutrena lists the starch and sugar in their Special Care feed? SafeChoice Special Care Horse Feed by Nutrena
The asterisk indicates that the NSC value is the starch and sugar values added together. This means that the NSC is about 15%... which isn't actually that low at all. Compare it to the NSC values that Triple Crown lists for its different feeds (I love
how transparent Triple Crown is with its nutritional info -- no asterisks to hide the actual facts!!) Triple Crown Horse Feed Carbohydrate Values With Fixed Formulas | Triple Crown Nutrition
Since IR horses do better with the lowest NSCs possible, I don't think that Safe Choice Special Care is your best option. Look at how low some of the Triple Crown NSC values are in comparison (even their Senior Feed is lower NSC!). In your case, I think Triple Crown 30% or Triple Crown Lite would be the best option for your horse. Their NSC values are way lower (around 9%) and they both give you much more "bang for your buck". Pound for pound, the Triple Crown products are packed with far, far more vitamins and minerals, which means you have to feed less of them to achieve the optimal nutrition for your horse.
If we were feeding a 1000 lb horse based on the recommendations for each of these feeds, this is how much they would need to receive:
Safe Choice Special Care: 5-7.5 lbs
Triple Crown Lite: 2-4 lbs
Triple Crown 30%: 1-1.5 lbs
As you may have noticed, I'm a bit biased towards Triple Crown feed products (I've been very pleased with how my horses have done on them)... but they aren't the only feed company that has higher quality, lower NSC, and more nutritious feed.