Countdown kitchen timer

Can anyone help explain why my timer correctly runs out to the full duration, however the countdown display on the dashboard always starts at 30 seconds less whatever I put in?

E.g for this 2 minute, (OK one second after hitting it!) I get this:
30

Or if it’s a 1 min timer, it displays 30 etc etc.

Then at the end of the last 30 seconds, just displays ‘Active’, then finally at the ‘real’ zero, switches to idle.

In other words, although it works correctly, the display is always 30 seconds fast.

This is my script to start the timeer:

alias: 'Timer Start Seth '
sequence:
  - service: timer.start
    data_template:
      entity_id: timer.seth_timer
      duration: 00:{{ states('input_number.timer_minutes') | int }}:00
mode: single
icon: mdi:alpha-s-circle-outline

The timer and input number are just very basic helpers.


Thanks!!