How to set text in datetimepicker with ngx-mat-datetime-picker in Angular

I am using the library ngx-mat-datetime-picker from angular-material-components to get datetime selection. It is working well so far, but I need to be able to set text in front of the hours and minutes, like 'HH' and 'MM'.

What I have is:

And what I am looking for is something like this:

Can someone help with that?

This is the code I have:

        <mat-form-field>
          <input matInput [ngxMatDatetimePicker]="dateStart" placeholder="Date Start" [(ngModel)]="dS" disabled>
          <mat-datepicker-toggle matSuffix [for]="dateStart"></mat-datepicker-toggle>
          <ngx-mat-datetime-picker #dateStart disabled="false"></ngx-mat-datetime-picker>
        </mat-form-field>