When it comes to software updates on Windows Phones, there are two types: OS and firmware. OS updates can be big like some GDR releases while others can be minor, like the current 14234 build. The same applies to firmware, which usually improves some aspects of the hardware like the display or camera.
Some new firmware for the Lumia 535 dual-SIM has been spotted on Navifirm, which hosts the updates before being pushed through to Microsoft’s servers. The firmware version is 15114, up from 15053, which was released a few weeks ago, bringing improvements to the touch display on the Lumia 535.