  We compute the macroscopic entropy of the supersymmetric rotating dyonic
strings carrying linear momentum in 6D (1,0) supergravity with curvature
squared corrections. Our calculation is based on Sen's entropy function
formalism applied to the near-horizon geometry of the string solution taking
the form of an extremal BTZ$\times S^3$. The final entropy formula states that
the two independent supersymmetric completions of Riemann tensor squared
contribute equally to the entropy. A further $S^3$ compactification of the 6D
theory results in a matter coupled 3D supergravity model in which the
quantization condition of the SU(2)$_R$ Chern-Simons level implies the horizon
value of the dilaton is not modified by higher derivative interactions beyond
supersymmetric curvature squared terms.
