Ratio of bleach to water required to disinfect COVID-19?
I have also been frustrated by use of percentages in protocols when making dilutions of stock bleach.  It's helpful to look at the product labels, as they often have dilution factors for different uses as well as concentrations in parts per million.  

I have a bottle of Clorox brand concentrated bleach sitting next to me, and the label says this solution is 8.25% sodium hypochlorite.  The label also says that 8.25% sodium hypochlorite yields 7.85% available chlorine, and that 4 oz. of this product in 1 gallon of water yields 2,400 ppm chlorine, implying that the stock concentration is 76,800 ppm if 1 gallon (128 oz.) is the total volume or 79,200 ppm if the 1 gallon is added to 4 oz. (that is, 132 oz. total).  For simplicity, let's say that the stock solution is 78,500 ppm so that 1% available chlorine is exactly 10,000 ppm chlorine.   

The CDC website cites a study that states 200 ppm chlorine is sufficient to inactivate 25 different viruses.  Sadly, I cannot find the text of that study.  Here's the citation:  

Klein M, DeForest A. The inactivation of viruses by germicides. Chem. Specialists Manuf. Assoc. Proc. 1963;49:116-8.

So, using the low end of your given values, a 3% stock solution of bleach will have ~2.85% available chlorine, following the yield ratio above.  Diluting 5 tbsp. (2.5 oz.) of this stock in 1 gallon of water (total volume 130.5 oz.), as recommended, will yield ~0.05% available chlorine, or 500 ppm, which is sufficient for viral inactivation.

Edit - a bulletin from Clorox (PDF, cached HTML) states that 2400 ppm available chlorine is recommended for disinfecting hard, nonporous surfaces.  The bulletin also lists enveloped and non-enveloped viruses against which this product is effective (at the "99.9%" level), including Human Coronavirus (Strain 229E, ATCC VR-740)