@Sativa The measurements allow you to fine tune your nutrients to see what works. Let’s say purely hypothetically you mix a feeding with a TDS of 500 and feed your plants and they end up with deficiencies so you double it to 1000 tds for the next feeding and they end up with surpluses you can use the measurement to fine tune it to about 750 tds to get a proper feeding without excess or deficiencies.
It makes it easier in the long run to measure TDS because it gives you a more accurate way to measure nutrients instead of ml per gallon etc.
One of the best things about TDS readings is if you find you mix your nutes too strong it let’s you see it and you can just dilute with more water to lower TDS until you reach your desired reading. The opposite also applies if you don’t have enough you just add some more nutes until the desired TDS.