What does this equation mean?

The scale of what needs to be canceled is worth stating plainly, using the same illustrative parameters as the previous section. The laser/center-of-mass term for a single-photon transition near 698\,$\mathrm{nm}$ ( $k_{\rm eff}$$\approx$9.00$\times$10^6\,$\mathrm{m^{-1}}$ ) scales as $k_{\rm eff}$g$T^2$$\approx$8.8$\times$10^{7}\,$\mathrm{rad}$ for T=1\,$\mathrm s$ . The recoil term for a strontium-mass atom ( m$\approx$1.443$\times$10^{-25}\,$\mathrm{kg}$ ) scales as $\hbar$ $k_{\rm eff}^2$T/m$\approx$5.9$\times$10^{4}\,$\mathrm{rad}$ . The clock term computed above is $\approx$0.29\,$\mathrm{rad}$ . Both confound terms are, respectively, roughly eight and five orders of magnitude larger than the signal, which is exactly why isolating $\Delta$$\phi_{\rm clock}$ is described in this literature as requiring careful differential design rather than being visible in a raw phase reading.