title: How can i sum up a char field in odoov11?
body: <p>I have this char field:</p>
  <pre><code>overtime = fields.Char(readonly=True, default='00:00')
  </code></pre>
  <p>I would need to summarize the values ​​of the overtime field, and I want to print this value in a new field.</p>
  <p>This is how the values ​​appear in the overtime field:</p>
  <pre><code>01:00
  01:00
  00:00
  03:00
  00:00
  02:00
  00:00
  00:00
  00:00
  02:00
  00:00
  </code></pre>
  <p>Is it possible to do it?</p>
  <p>Thanks for your help!</p>
  <p>Regards,</p>
  <p>Steven</p>