If the electroscope has a deficit of electrons, it means that the electroscope is charge positivelly.
The charge of the electroscope is equal to the equivalent charge to the deficit of the electrons.
Use the following equivalence:
1 C = 6.24*10^18 electrons C is the unit coulomb for the charge
Then, for the given amount of electrons, you obtain:
Hence, the charge of the electroscope is approximately 6.4*10^-8 C