Displaying a divided value

I am taking my first steps on Home Assistant and I am stumbling upon a seemingly simple problem, in a dashboard card I want to display the value of an entity divided by 10.
This is the consumption of the day of my heat pump. (energy_1)
The entity is generated by MQTT Discovery. I do not have the possibility to modify this value at the source, it is 10 times too high.

With the UI interface on both the cards and the MQTT entities there is no division (or multiplication) factor field provided. This is a shame.

I tried to tinker with customize and value_template in configuration.yml on the entity but without results.

Below is the content of the MQTT config message received.

How to solve this problem?

Transmitted messages:
ebusd hmu State energy_1 (sensor.ebusd_hmu_state_energy_1)
MQTT discovery data:
Topic: homeassistant/sensor/ebusd_hmu_State_energy_1/config
Payload
unique_id: ebusd_hmu_State_energy_1
device:
  identifiers: ebusd_hmu
  manufacturer: ebusd.eu
  via_device: ebusd
  sw_version: '24.1'
  suggested_area: Heating
  name: ebusd hmu
value_template: '{{value_json["energy_1"].value}}'
state_topic: ebusd/hmu/State
unit_of_measurement: kWh
state_class: total_increasing
device_class: energy
name: State energy_1
Subscribed topics:
ebusd/hmu/State
10 most recently received messages
Received 6:15:21 PM
QoS: 0
Payload: energy:
  value: 19
energy_1:
  value: 305
onoff:
  value: 'on'
state:
  value: heating