Strictly speaking in a "Worst Case" Scenario., you're only using around 210MB V-RAM (30MB S-RAM) assuming that you're using Full Precision Floating-Point (R32) Encoding.
With this said., it's difficult to speak in regards to how this is being handled via the AppGameKit Studio (Vulkan) Engine and Asset Management System.
This isn't strictly aimed at you, but rather the TGC Development Team... but one of the key issues *A LOT* of Development Studios are having when switching from Classic Graphics API (SDL, OpenGL, DirectX 11 or Below) is that Memory used by Asset Management and Generation was handled entirely internally via the Graphics API (well Graphics Drivers).
A result of this is Developers switching from HAL to CTM APIs, while they might be fairly well versed in System Memory Management have NEVER touched Video Memory Management essentially during their entire Careers., and so will typically overlook (or for performance reasons) omit typical Garbage Collection and/or be much more prone to Memory Leak Operations.
Now there's also another factor at play, being that Windows Virtualisation means you have to be sure to request what you need prior to commit.
This is why most Games will Reserve basically you're entire V-RAM., when they might only use like 1.5 - 3.0GB of it... because if they don't Windows will be like "Oh Free Memory... Om Nom Nom Nom" (especially if you have a Browser Running in the background., like YouTube or something)
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Oh and as a quick side note., for better Memory Management (and GPU Performance) I'd strongly suggest getting the Intel DDS Tools for Photoshop CC (NVIDIA's tools are woefully out-of-date) as well as AMD's Compressonator Application.
As Compressing Images doesn't just mean that they'll use less Space., but if you use a Native Compression Format for the Target GPU, it no longer has to spend time converting to a Native Format.
PNG/TGA/TIFF is good for Development Purposes (due to being "Raw" Formats without Compression Artefacts., plus they don't take long to Calculate Save and MIPs) but for actual Production Ready., you want to switch unless you need portability (say PNG for HTML5).
And for those working with 3D., AMD's Tootle Application is great for Vertex Efficiency Ordering, Optimisation as well as Tessellation Optimisation for both Traditional and Tiled Rendering.