`timescale lns/lns

This command is used in Verilog or SystemVerilog to specify the time scale for the simulation. The `timescale` directive defines the time unit and time precision used in the simulation.

In this case, `lns` is used as the time unit and `lns` is used as the time precision. `lns` stands for "logarithmic nanosecond" and is a commonly used time unit in Verilog/SystemVerilog simulations.

The time unit defines the basic unit of time used in the simulation, while the time precision specifies the smallest time increment that can be represented. For example, a time unit of `1ns` and a time precision of `1ps` means that the simulation can represent time increments as small as one picosecond within a one nanosecond time unit.

Overall, the `timescale` directive is an important part of setting up a Verilog/SystemVerilog simulation and helps ensure that the simulation accurately models the timing behavior of the design being tested.