Relative populations of the three energy-lowest isolated-pentagon-rule isomers of Ho@C82 under high-temperature synthetic conditions are computed using the Gibbs energy based on characteristics from the density functional theory calculations (B3LYP/3-21G~SDD entropy term, B3LYP/6-31G*~SDD energetics). Two major species are predicted, Ho@C2v;9-C82 and Ho@Cs(c);6-C82, with rather comparable populations under supposed synthetic temperatures. Roles of the inter-isomeric thermodynamic equilibrium and solubility are discussed.