Odd Transform Behavior in Inspector Window...

Or total n00b mistakes.

I'm brand-spankin' new to apps such as Unity so this could be a rookie mistake. However, all signs are pointing to odd behavior from the app.

I've created a cube that I've scaled to be long and thin so it can act as back wall to a building I'm creating. When working with the Transform panel in the inspector window, it appears as if values are randomly changed on me.

The cube will be perfectly aligned, yet not quite long enough, so I will edit the X scale from a "90" to a "91" and suddenly, my cube has rotated 90 degrees along an axis or two.

I'll give an example.

Currently position has these 3 values: 45/13/0
Rotation is -0/-90/90
Scale is 91/1/25.

If I highlight the "91" in scale and change it to "90" and tab to the next box in the Transform panel, it jumps the rotation on the figure.

If I deselect and reselect the object the new stats are as follows: Position is 45/13/0
Rotation is 90/90/0
Scale is 90/1/25.

What's up with that sudden rotation jump?

I'm likely leaving out crucial details, so let me know what I need to fill in. The cube is unaltered beyond changing its basic properties in the inspector window.

Thanks.