I assume you are talking about static or transient structural analysis. The initial, maximum, and minimum time step is referring to the substeps. A step can consist of several substeps, and if you define the initial step, max, and min substep size, your substep will start at the initial value, and varies within the min and max values. This is based on you have turned on "automatic time stepping" and the solver will adjust the substep size to optimize the simulation speed.
This website has a very detailed description of step and substep definitions: https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v193/wb_sim/ds_Steps_Substeps_Eq.html
This website has a guideline for integration step size (in other words, how to choose sub-step size): https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v193/wb_sim/ds_guidelines_int_time.html
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