The other answer by @SoulEater asserts that the numbers refer to the octave of the note. This is incorrect, so I am adding my own answer here to address the OP's question.
The sapta swarās, namely Sa, Ri (or Re), Ga, Ma, Pa, Dha and Ni, are employed in a 12-note system in Hindustani music and in a 16-note system in Carnatic system.
In Hindustani music, what this means is the following: Sa and Pa are "fixed" notes, and there are two positions for each of Re, Ga, Ma, Dha and Ni. These give rise to the
2 + 2x5 = 12 notes in the Hindustani system.
In Carnatic music, what this means is the following: Sa and Pa are "fixed" notes, and there are three positions for each of Ri, Ga, Dha and Ni, and two positions for Ma. These give rise to the
2 + 3x4 + 2 = 16 notes in the Carnatic system.
Now, the 12 notes in the Hindustani system are given the following names (listed in increasing order of the pitch):
- Komal Re
- Shuddha Re
- Komal Ga
- Shuddha Ga
- Shuddha Ma
- Tivra Ma
- Komal Dha
- Shuddha Dha
- Komal Ni
- Shuddha Ni
(It might help to "visualise" the positions of these swarās if you note that they correspond to the movable Do Re Mi in Western music, as mentioned in @AlbrechtHügli's answer to this question of yours: Equivalency between Indian Classical Saptak and Western Notes.)
An alternative way to notate these 12 positions is to simply number the different positions of Re, Ga, Ma, Dha and Ni, as follows:
So, for example, Bilawal Thaat (corresponding to the rāgam Sankarābharanam in Carnatic music, or to the major scale in Western classical music), uses the swarās
S, R2, G2, M1, P, D2 and N2
Similarly, in Carnatic music, we give names to each of the 16 notes, and we also refer to them in short by adding numbers to the swarās as before. In increasing order of pitch, they are as follows (I am not mentioning their names here):
- R2 = G1
- R3 = G2
- D2 = N1
- D3 = N2
As you can see, the 16 notes do not have distinct positions. In terms of their pitch, R2 is the same as G1, D2 is the same as N1, etc.
Aside: note that some restrictions clearly have to be placed. Since a ragam must not have a rishabham and a gāndharam both of the same pitch, if R2 occurs in the rāgam, then G1 will not occur, and vice-versa. Similarly for the other overlaps. Moreover, the gāndharam cannot have a lower pitch than the rishabham, so if R3 occurs in a rāgam, then G1 cannot occur. Again, similar restrictions apply to the dhaivatam and nishādam.
Now, to answer the main question, the equivalence between the two systems of notation shows that the notes
S, R2, G2, M1, P, D1 and N2
Sa, Shuddha Re, Komal Ga, Shuddha Ma, Pa, Komal Dha and Komal Ni
Warning: if you see someone notating the swarās using subscripts, as in the linked video, then know that a priori they could be using either the 12-note system or the 16-note system. So, things can get confusing because, for instance, G2 means two different things in the two systems! Also know that the 12-note system is sometimes used in Carnatic music as well, so just knowing that a piece in Carnatic music is being notated is not enough to be sure which of the two notation systems is being used.
A good place to start if you want to know more about the notations used for swarās in Indian classical music is the Wikipedia article on swarās.