so does it mean if it says 1+14 is that 100ml chemical and 1400ml water
That would be correct.
If the instructions say "A + B", you take A-parts of stock solution and mix it with B-parts of clean water. You will end up with A+B amount of working solution at the end.
It doesn't really matter what the units of measure are as long as you are consistent throughout. You could use milliliters, ounces or drams. You could even use Dixie cups if you wanted to be so silly. Just be sure that you use the same units of measure for everything and be sure to measure as accurately as you know how.
In your example, you use 1 unit of stock and 14 unit of water to end up with 15 units of working solution: 100 ml. of chemical gets added to 1,400 ml. of water and you will end up with 1,500 ml (1.5 liters) of ready-to-use solution.
If you want to measure in ounces, you would add 1 oz. of stock to 14 oz. of water to get 15 oz. of working solution.
You can run the calculations backward, too. If you need a certain amount of working solution, you can calculate how much stock and how much water you need to make it. Just add the two numbers together and divide.
If you need 1.5 liters of working solution (1,500 ml.) and you know that your recipe calls for "1 + 14", add those numbers together to get 15 then divide that into 1,500 ml. The answer is 100 ml. Therefore, you need 100 ml. of stock. Subtract that from the total amount of solution and you calculate the amount of water needed. (1,500 - 100 = 1,400)
Double check your math. Does 100 + 1,400 = 1,500? Does that match with the numbers called for in the recipe? Yup! You're good to go.