A game that I learn

I was taught a game that I wanna share with you all. See the pictorial below and guess the subsequent number.

The photo above showed 5 fingers, but I will say this is 3.

Then I showed you this, and I said it is 5

Then I said this is 2.

And now I said this is 4.

Finally I said this is one.

a) Now, I showed you this. What number should it be??
b) And how bout this??
c) And this??

I bet most of you will know after looking at the photos awhile. It's not that hard though when u can repeatedly scroll up and down. :p

Happy guessing!!