Loaches Online Forum

I have the API test with the drops, but the chart confuses me because it's one chart for both KH and GH. If it takes 3 drops to turn for KH and 8 drops for GH, does that mean my KH is 53.7ppm and my GH is 143.2 ppm? Are those numbers kind of low and high respectively?

That is right.
The tests are completely independent, but they work the same way.

However many drops until it changes color, that is how many German degrees of hardness.
Multiply by 17.9 to get ppm or mg/l.

It is entirely possible for the GH and KH to be widely different.

GH is a test of Calcium and Magnesium. These are required minerals by plants and fish. Fish are adapted to different levels of GH. Research the fish you want to keep, and make sure the GH of the water is within their range. Their metabolism is adjusted to the water they evolved in.
Fish kept in water that is too hard can accumulate too much calcium and it can kill them.
Fish kept in water that is too soft can become deficient in minerals.

KH is a test of carbonates (that is, carbonate and bicarbonate). These are a buffer that stabilizes the pH.
If the KH is high the pH will be stable, and tends to be high.
If the KH is low the pH is not stable, and may tend to be low, but can be high. It is easily altered by minerals, salts, acids and similar materials.