In principle, $\mathcal{N}$ gives you the number of supercharges in your theory. There are, however, cases with more than one irreducible (pseudo-)real spinor representations. If you have $N$ charges in one and $N'$ charges in the other representation, you can denote the total number of charges as $\mathcal{N}=(N,N')$ in order to emphasize the difference. Examples would be $\mathcal{N}=(1,1)$ type IIA supergravity in ten dimensions or $\mathcal{N}=(2,2)$ supergravity in six dimensions. But there also exists notation in which the latter is referred to as $\mathcal{N}=4$.

In principle, $\mathcal{N}$ gives you the number of supercharges in your theory. There are, however, cases with more than one irreducible (pseudo-)real spinor representations. If you have $N$ charges in one and $N'$ charges in the other representation, you can denote the total number of charges as $\mathcal{N}=(N,N')$ in order to emphasize the difference. Examples would be $\mathcal{N}=(1,1)$ type IIA supergravity in ten dimensions or $\mathcal{N}=(2,2)$ supergravity in six dimensions. There also exists notation in which the latter is referred to as $\mathcal{N}=4$.

In principle, $\mathcal{N}$ gives you the number of supercharges in your theory. There are, however, cases with more than one irreducible (pseudo-)real spinor representations. If you have $N$ charges in one and $N'$ charges in the other representation, you denote the total number of charges as $\mathcal{N}=(N,N')$. Examples would be $\mathcal{N}=(1,1)$ type IIA supergravity in ten dimensions or $\mathcal{N}=(2,2)$ supergravity in six dimensions.

In principle, $\mathcal{N}$ gives you the number of supercharges in your theory. There are, however, cases with more than one irreducible (pseudo-)real spinor representations. If you have $N$ charges in one and $N'$ charges in the other representation, you can denote the total number of charges as $\mathcal{N}=(N,N')$ in order to emphasize the difference. Examples would be $\mathcal{N}=(1,1)$ type IIA supergravity in ten dimensions or $\mathcal{N}=(2,2)$ supergravity in six dimensions. But there also exists notation in which the latter is referred to as $\mathcal{N}=4$.