Recently, the BTZ black hole in the presence of the gravitational Chern-Simons (GCS) term has been studied and it has been found that the usual thermodynamical quantities, like as the black hole mass, angular momentum, and black hole entropy, are modified. But, for large values of the GCS coupling, where the modification terms dominate the original terms, some exotic behaviors occur, like as the ... [Show full abstract] roles of the mass and angular momentum are interchanged and the black hole entropy depends more on the $inner$-horizon area than the outer one. A basic physical problem of this system is that the form of entropy does not guarantee the second law of thermodynamics, in contrast to the Bekenstein-Hawking (BH) entropy. Moreover, this entropy does $not$ agree with the statistical entropy, in contrast to a good agreement for small values of the GCS coupling. Here I find that there is another entropy formula where the usual BH form dominates the inner-horizon term again, as in the small GCS coupling, such as the second law of thermodynamics can be guaranteed. I compare the result of the holographic approach with the classical- symmetry-algebra-based approach and I find exact agreements even with the higher-derivative term of GCS. This provides a non-trivial check of the AdS/CFT-correspondence in the presence of higher-derivative terms in the gravity action.