There’s a good chance you’re not using the test kit properly based on your comments. You’re best off using a 20ml sample. You can put it in a small cup e.g an espresso cup.
Shake the bottles for testing KH and GH. Completely invert the bottles to make sure the drops are the same each time, if you hold the bottles at an angle you’ll get inconsistent results as you add each drop. Stir the sample after each drop (I just stir continuously and add the drops every 5 seconds or so). You probably won’t get too much colour at all in the samples with the amount of reagent you’ll be adding. You don’t keep adding until you get a “bright” colour, you stop at the first sign of colour change.
It’s also good to understand what the kit is measuring. Take your GH for example. You have a set of instructions that tell you 1 drop = 17.9mg/l (as in the colour just changes immediately). With the 5ml sample you know that you have anywhere from 0-17.9mg/l Hardness. If it takes two drops you know you have between 18mg/l - 35.8mg/l etc. With a 20ml sample the accuracy of the test increases x 4 e.g. 4 drops = 17.9 mg/l so the range you are measuring is reduced to +/-4.475mg/l compared to +/- 17.9mg/l.
If you’ve added 0.36g Sodium Bicarb to 5l water you should have an alkalinity of 43.5mg/l
0.1g in 1 litre is just about 60mg/l………you have measured your alkalinity to be 53.8mg/l - 71.6mg/l
Your second attempt was obviously more successful.