Why doesn't the Radix Ledger app show the exact amount when I am unstaking?

Russell from Radix provided a comprehensive explanation as follows:

  • Stake on nodes is not stored as an amount of XRD, but a number of StakeUnits.
  • The XRD amount corresponding to a 1 StakeUnit differs from node to node. Presently, all nodes start their life at 1 XRD per 1 StakeUnit, but network emissions will adjust this number over time.
  • When you announce an intent to stake 1000 XRD to BobNode, a calculation is made that says “Well, as of this epoch 1 StakeUnit on BobNode is 1.02 XRD. You can only get a whole number of StakeUnits. Closest I can come is for you to get 980 StakeUnits, which currently works out to 999.6 XRD, so that’s what we’ll do.”
  • At epoch rollover, when emissions happen, if BobNode qualified for emissions, the network increases the value of a StakeUnit on BobNode. To keep the math simple, let’s pretend that increased to 1.03. Your “amount staked” shown for BobNode would now be 980 * 1.03 = 1009.4

What you’re seeing on your Ledger when unstaking is actually the number of StakeUnits, not the amount of XRD.

Ref: Discord