Non-Hermitian degeneracies, also known as exceptional points (EPs), have been the centre of much attention due to a singular eigenvalue surface structure thereabout. Still, pertaining to a non-Hermitian metasurface platform, the reduction of an eigenspace dimensionality at the EP has been investigated only in a passive repetitive manner. Here, we propose an electrical and spectral way of resolving chiral EPs and clarify the consequences of chiral mode collapsing of a non-Hermitian gated graphene metasurface. More specifically, the measured non-Hermitian Jones matrix in parameter space enables quantifications of nonorthogonality of polarization eigenstates and half integer topological charges associated with the chiral EP. We further show that the output polarisation state can be made orthogonal to the coalesced polarisation eigenstate of the metasurface, revealing the missing dimension at the chiral EP. It is also found out that the maximal nonorthogonality at the chiral EP leads to the blocking one of the cross-polarised transmission pathways and consequently, the observation of enhanced asymmetric polarisation conversion. We anticipate that electrically-controllable non-Hermitian metasurface platforms can serve as an interesting playground for the investigation of rich physics related to the chiral EP.