The 100 ml format is well suited if you want to try the shampoo before committing to a larger bottle, or if you need a smaller size for travel or a gym bag. Since scalp comfort and oiliness are individual, a trial size can be helpful: you can see whether the cleansing level suits your roots without immediately changing your whole hair routine.
When testing it, keep the rest of your routine as consistent as possible for several washes. Use the same conditioner, styling products and washing frequency, so you can judge the shampoo itself more accurately. Focus on practical signs: whether the roots feel clean after rinsing, whether the scalp feels comfortable rather than tight, and whether the hair becomes heavy at the roots as quickly as before.
Because this shampoo is intended for balancing oily or mixed scalps, apply it mainly to the root area. If you use too much product or massage it through the full lengths each time, dry ends may feel less comfortable, which would not reflect the best way to use it.
For travel, keep the bottle closed tightly and store it away from direct sunlight. As with any shampoo, avoid contact with the eyes and rinse immediately with water if it gets into them.