Hik Thermal 26XX series firmware

Hello, was wondering if you could help on firmware for the DS-2TD2615-10. Currently i'm running v5.5.18 build 191202, on the EU download portal v 5.5.8 is available but it has a build version of 181221 which is significaly older than the build date of the firmware installed. Also for v 5.5.18 the camera module firmware for our D1 module is 5.5.18 where as for firmware version 5.5.8 the camera module firmware is 5.5.16.

So my question is which is the newer firmware is it by build date or by...

Hik Thermal 26XX series firmware