I'm googling 'brine shrimp salt requirement' to find answers to your question, and I'm finding a lot of results.

1. This looks like a good site for hatching brine shrimp eggs:
link 1

It says this about salt:
25 parts per thousand (ppt) salt solution, or approximately 1 and 2/3 tablespoons of salt per quart (or liter) of water. This equates to around 1.018 specific gravity as measured with a hydrometer. Be sure to use marine salt or solar salt.

2. Another site says this:
Prepare saline solution by dissolving 25 grams of salt in an Imhoff transparent cone of 1 liter or 1000 ml of water (25 grams of salt is equal to about one heaping table spoon). Add a pinch of baking soda as a buffer. A pH of 8.0-8.5 is optimal and the baking soda should take care of this.

3. This is what the 3rd site says:
The less salt in the water, the easier it is for brine shrimp to absorb enough water to burst through their protective shell. But, specific gravity should be at least 1.011 (15ppt) and can be as high as 1.030 (40ppt). This means that if you're Hatching in 1 quart, or liter, of ordinary tap water you should add somewhere between 1/2 and 2 level tablespoons of salt. The pH of the water should also be between 8.0 and 8.5. If your pH is below 8.0 your hatch rate will drop dramatically.

4. Here's what the 4th site says:
Salinity:
Approximately 11/2 tablespoons of salt per quart (or liter) of water. This equates to about 1.018 specific gravity as measured with a hydrometer. Aquarium, sea or non-iodized table salt can be used.

pH:
Proper pH is important in hatching brine shrimp. A starting pH of 8.0 or higher is recommended. If the pH of your water is below 7, Epson salt or baking soda can be added at the rate of 1/2 teaspoon per quart.

5. My conclusion:
The recommendations are fairly similar, thoigh I'm guessing there's a typo in #3, and it should probably say '1-1/2 to 2 tablespoons' salt, not 1/2 to 2.

I like #4, because it says gives a better recipe for how to adjust the pH.