Science with Arthur C. Clarke (1)

In Chapter 1 of 2010: Odyssey Two, Arthur C. Clarke wrote that an astronaut achieved a tenth of the speed of light in less than two minutes, and this meant an acceleration of about a quarter of million gravities.

Let's check. Here, I feel that the term "gravity" is not technical enough: Does it mean $1~\mathrm{ms}^{-2}$, the unit acceleration in SI units? Or g-force, an acceleration of about $9.8~\mathrm{ms}^{-2}$?

Given that:

$$u = 0~\mathrm{ms}^{-1} \\ v = \frac{c}{10} \approx 3.0 \times 10^7~\mathrm{ms}^{-1} \\ t=120~s$$

We have:

$$a = \frac{v-u}{t} = \frac{3.0 \times 10^7}{120}~\mathrm{ms}^{-2} \\ \approx 250,000~\mathrm{ms}^{-2}$$

Indeed! The term "gravity" here should mean $1~\mathrm{ms}^{-2}$, which is the unit acceleration in SI units.