Allocation size scale factor for the buffer used to store instances after culling.
The total size accounts for the worst-case scenario in which all instances are emitted into every clip or mip level.
This is far more than we'd expect in reasonable circumstances, so this scale factor is used to reduce memory pressure.
The actual number cannot be known on the CPU as the culling emits an instance for each clip/mip level that is overlapped.
Setting to 1.0 is fully conservative. Lowering this is likely to produce artifacts unless you're certain the buffer won't overflow.
