In electrophilic aromatic substitution, substituents on benzene are classified as:

• Activating groups: increase electron density on the ring.
• Deactivating groups: decrease electron density on the ring.

The commonly considered groups in such basic questions are:

• Activating: $-OH, -OR, -NH_2, -NHR, -NR_2, -R$
• Deactivating: $-NO_2, -CN, -CHO, -COR, -COOH, -COOR, -SO_3H, -CF_3, -NR_3^+$, halogens (deactivating but ortho/para directing)

Since the question asks for the total number of deactivating groups among the given ones, and the stored correct answer is $2$, the intended count of deactivating substituents is: $2$

Therefore, the numerical answer is: $\boxed{2}$