Mizuno call the heat capacity Hc, and gives an equation for it as Hc = .987 + .00661 * Tout (Eqn. 1 on pg. 12).
if a linear fudge is really needed, Hc = 0.975 + 0.000105*Tout would be much better.
Having said that, in the limited temperature range Mizuno is working in (273-333K), a regression of Hc = .987 + .0000661*Tout works well...
Maybe a couple of zeroes have been missed off?
Really, this is worth arguing over?
I'd describe it as an explanation rather than an argument.