I hate to be the bearer of bad news but I don't think either of your calculators will work.
With the 1st one, decreasing the HCl%, it seems you are starting with 32% HCl, by weight, and are converting it to 10%, by volume. I can tell this because (10/32) X 100 = 31.25 and that is a by volume (not by weight) calculation. In other words, you are mixing apples and oranges. To convert 32%, by weight to 10%, by weight, it would take 28.2 ml of 32% HCl and 71.8 ml water. With your use of 31 ml of 32% HCl + 69 ml H2O, you would end up with 11%, by weight, HCl. It's not off much in this case but, with certain combinations, your method would have had much greater error. For example, If you dilute 70% nitric, by weight, with an equal amount of water, you end up with 40-41% nitric, by weight, not 35%. You could say that this is 35% nitric, by volume, assuming you identified your starting point of 70% nitric, by weight.
Using this chart:
http://www.handymath.com/cgi-bin/hcltble3.cgi
All at 20C, 100ml of 32%, by weight, HCL, will weigh 115.93g. 100ml of 10% will weigh 104.74g. 100ml of 32% contains 115.93 X .32 = 37.1g of HCl. 100ml of 10% contains 104.74 X .10 = 10.47g of HCl. Therefore, it will take (10.47/37.1) X 100 = 28.2ml of 32% HCl + 71.8ml of H2O to produce 10% HCl, by weight.
The basic reason your 1st calculator didn't work is because you are working with 2 different things, HCl and water, and these have different specific gravities (weight per unit volume). Weight-wise, if you increase one it will not be the same weight gain as the weight loss of the other even though the volume gain of the first will equal the volume loss of the other. It's more complicated than you gave it credit for. The only time a percentage change, by weight, would equal the same percentage change, by volume, would be if the 2 ingredients had identical specific gravities.
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The 2nd chart, increasing the HCl percentage, won't work at all, as Dave said. HCl is a gas dissolved in water. At 32% HCl, I believe a greater percentage of the HCl will be evaporated than water. In other words, instead of increasing the HCl percentage by applying heat, you will decrease it. The azeotrope of HCl is 20.2%. As I understand it, when evaporating, 20.2% is what it will strive for. I'm really not too well versed on this. Maybe Richard Butcher can chime in on this.
With sulfuric acid, you're able to evaporate battery acid (~35% H2SO4) to increase the by weight percentage to about 98%, which is the H2SO4 azeotrope, assuming I really understand what azeotrope means.