Is anyone else working through this paper: A theory of generalized Donaldson-Thomas invariants, by Dominic Joyce, Yinan Song? I am trying to verifying example 6.2 (m=2 for simplicity) using only the definitions, namely:

J^{2\alpha}(\tau) = -1/4

(where \alpha satisfies M^{\alpha}_ss = M^{\alpha}_st and that Ext^1(E, E)=0 for any E \in M^{\alpha}_ss and finally that the only object of M^{m\alpha}_ss is E ^{\oplus m})

I keep getting -3/4. Has anyone else attempted to make such a computation? Did you get the answer you are supposed to get?