Unusual Healing Powers

I have been feeling that some of my ships were healing at an abnormally fast rate so I decided to capture an instance where that happened.  The first screen snapshot below shows that I have an Assent M5 that only has 1 hit point (I just scavenged it in a battle).  the second screen snapshot shows an Iconian Sand that is right next to my Assent M5.  When I attack the Iconian Sand with my Assent M5 I am victorious and, as the third screen snapshot below shows, my hit points have increased to 29!  How can that happen?

The battle report, shown in the fourth screen snapshot below, shows that I killed the Sand with my first shot, but it also shows that the Sand did 2 damage to my Assent.  Given that the Assent started with only 1 hit point shouldn't it have also been destroyed?  If there is some logical reason why it should have survived, what is the reason for it to gain hit points, up to 29?