The program can be set to either US or metric units. This is selected under "More Calcs" and "Settings"
Chlorine Strength is the concentration of the Sodium Hypochlorite (bleach) you are using. Regular bleach is 5.25%, ultra bleach is 6%, and liquid shock is either 10% or 12%. Enter this as a number, e.g. 5.25 for 5.25% bleach.
PPM Increase Desired is how much you want the TC to increase. You can either enter this value or the Quantity of Bleach, and the program calculates the other.
The grayed out blanks are for results. The bleach amount is calculated in gallons, quarts, cups and ounces for easy measuring, and the OR box indicates the amount in gallons only, e.g. 1 Gallon(s), 1 quart(s), 1 cup(s) and 3 ounce(s) OR 1.3 Gallon(s).
Without knowing how much water your pool holds, I can't provide any details.