Win 10 (64)
Short description of error
Particle instance stores indices from default Cube in vertex color layer. Then this data is transfered back to Cube via Data Transfer Modifier.
Color picker in "Vertex paint" mode shows maximum value as 0.875 which is closer to 7/8, but it is expected to be 1.0 or in other words 7 / (total vertex count - 1).
For comparison there is a multiplier color layer with 0.875 value (unmute "Divide" node).
Exact steps for others to reproduce the error
Open file, go to Vertex paint, color pick values with muted/unmuted "Divide" node