Amount of Phenolphthalein required We just had chemistry practical few days a go. The topic was strong acid-base titration, in which we had to find the normality and concentration of $\ce{HCl}$.

My teacher instructed me to add 2 drops of Phenolphthalein  in 10 ml $\ce{HCl}$, and then add $\ce{NaOH}$ from buret and take a reading.

We needed to repeat the process 4 times and then find the constant reading, but in that I never used to take 2 drops of Phenolphthalein, instead I used to take 5-6 drops and then also used to get almost same reading as of pilot reading.

So my question is whether it is compulsory to take 2 drops of Phenolphthalein or it was just a instruction so students don't waste it?

In this same instruction given. (Procedure point 2)
Using a little extra phenolphthalein won't matter. You just need enough so that the color is visible once the pH becomes basic enough. If you were titrating a large volume, you might need more than a couple of drops, but 2 drops is enough to be sure that the color will be visible in a typical lab-scale titration vessel. One drop would probably even work. The reason they say "two drops" and not "at least two drops" is that they don't want you to be wasteful.