The details of the changes in the firmware were revealed by Nokia Developer in a blog post a fortnight ago:

In addition, Nokia Lumia 620 has some new software in the pipeline. This software, version 1030.6407.1308.00xx, will include improved touch behavior and enhancements to system stability and camera picture quality, such as corrected camera exposure when the flash is used in bright light conditions.

The new firmware enables a number of features necessary for other, optional, app-based software updates. The most noteworthy of these is the addition of a "storage check" module in the Settings app, which we explained in an earlier post:

Storage check, which is specific to Nokia Lumia devices, provides a more detailed breakdown of a phone's internal memory than the existing standard phone storage module. It also allow for users to manually delete temporary files, which should help alleviate the "other" storage issue that sees the the amount of space occupied by "other" files, as shown in the phone storage module, grow over time.

You will only see the storage check module if you have the latest version of Nokia's "extras+info" Settings app module installed. 

Availability

The 1308 firmware is now shipping on new Lumia 920, 820 and 620 devices. The update is now rolling out to all Nokia Lumia 620 devices. The update was also rolled out to some Lumia 920 devices, but the roll out for LTE devices (Lumia 920 and 820) was halted due to some updated devices experiencing connectivity issues. This halt is expected to be temporary, with the updates expected to resume shortly.

The firmware is a Nokia specific update and is not tied to a Microsoft platform update. That means the OS version, 10211 (Windows Phone 8 GDR 1) will remain the same. Once the software update becomes available your device will let you know about any update automatically, but you can also check manually using the phone update module of the Settings app. We'll also post a story once the software update starts to roll out.