# What are the global symmetries of $\mathcal{N}=2$ SYM before twisting and after twisting?

I am confused with the global symmetries of $\mathcal{N}=2$ SYM. On one hand I know that the theory has a $U(2)_R = SU(2)_R \times U(1)_R$ symmetry. Now, there exists also a $U(1)_B$ global symmetry. What are the rest of global symmetries?

Additionally, something that confuses me is something on the lecture notes of Marino on Donaldson-Witten theory. In these lecture notes in section 6.2 the topological twist is being performed and I am very confused on how $K'=SU'(2)_{+} \otimes SU(2)_{-}$ is obtained (after the twist) and where it comes from.