Solarwinds Discovery Agent versions / updates

When I first deployed our Agent it was v2.0.7_2.0.5_1027_439
I assume once installed, the clients auto-update themselves, and can see the vast majority of our fleet is now on:
v2.0.7_2.0.5_1039_447

However when I check the version of the installer available from:  SWSD > Setup > Discovery & Assets > Installation Discovery Agent, I find:
v2.0.13_2.0.5_1039_447

Can you please explain the version number difference/s, and if there's any point upgrading to v2.0.13_2.0.5_1039_447 ?

Cheers :)