A confusion in the PLUMED histogram documentation

[erwushth]

Hi, When I read the histogram documentation, I found a description about kernel density estimation description as:

"In PLUMED the value of ζ at each discrete instant in time in the trajectory is accumulated. A kernel, K(ζ−ζ(t′),σ), centered at the current value, ζ(t), of this quantity is generated with a bandwidth σ, which is set by the user. "

https://www.plumed.org/doc-v2.9/user-doc/html/_h_i_s_t_o_g_r_a_m.html

Should the current value ζ(t) be ζ(t')(has apostrophe)?

Thank you!