Yeah, that’s not enough bolus insulin, for sure.
Given the duration of fast-acting is 3-5 hours (3.5-4 works for most people), you should dose so that you get back close to your fasting target within 3-4 hours. If you’re not, you’re not taking enough bolus insulin.
As I said in an earlier post, the only way to do this is to learn to count carbs and dose bolus based on an IC ratio. Once you have this figured out, you can confidently “blindly” bolus based on these calculations, and be safe and on target most of the time.
Otherwise, unless you eat a regimented, pre-calculated food menu, you’ll just be guessing most off the time, in which case everyone’s tendency is to do exactly what you’re doing – underdose.