This is where the TDS meter will come in handy and make things easy. (And part of the reason we recommend shrimp keepers get one).
With a TDS meter you just add enough of the dissolved mix into the tank (or water change) until it reaches 150TDS as measured with the TDS meter.
Without a TDS meter, just follow the instructions and dosage below:
Instructions of use
Mix with water outside of the aquarium. Shrimp Mineral dissolves almost completely within seconds, and the water is ready for use at once. Please make sure that any undissolved particles go into your tank, too. Close container after every use at once as this mineral salt absorbs moisture.
Dosage
Use Shrimp Mineral to re-mineralise RO water, rainwater, fully desalinated water etc. to reach a total hardness of about 6 GH and/or a conductance of about 300 +/- 50 uS (Microsiemens). For this purpose, an evenly full measuring spoon (about 2 g) to 10 litres (2.2Gallon) of water is sufficient.
While not as accurate without a TDS meter, it will get close. You can always adjust the TDS reading after you get your TDS meter.
Weekly water changes of 10% as per normal, with the new water adjusted to 150 TDS with SS GH/KH+.
If it is particularly hot and you notice the water level of the tank dropping, you top off with pure RO or Distilled water, no remineralising needed.
In summary,
Water Change = Add SS GH/KH+.
Top Off = straight distilled.