How to delete first&last characters ... but just numbers
<p>I have 10000 sites of text and basically it is subtitle-text... I want to delete of every line the last <strong>5 numbers</strong> and the <strong>first 2</strong> numbers without touching/changing the text...</p>

<p>Here is an example:</p>

<blockquote>
  <p><strong>18:</strong>      00:03:13:05 00:03:16:17 <strong>03:12</strong> Moi, j'aurais mis ça à la même hauteur que ça.</p>
  
  <p><strong>19:</strong>      00:03:18:02 00:03:21:05 <strong>03:03</strong> Dans un premier temps, je termine.</p>
  
  <p><strong>20:</strong>      00:03:23:15 00:03:26:07 <strong>02:17</strong> Ah, toujours le travail !</p>
</blockquote>

<p>The bold numbers should be deleted.</p>