Use sensible maths for from_rational.

paritytech/substrate#13660

pallets/runtime/tests/src/staking/mod.rs

@@ -6103,7 +6103,7 @@ fn proportional_ledger_slash_works() {
     ledger.active = unit;
     ledger.total = unit * 4 + value;
     // When
-    assert_eq!(ledger.slash(slash, 0, 0), slash - 5);
+    assert_eq!(ledger.slash(slash, 0, 0), slash);
     // Then
     // The amount slashed out of `unit`
     let affected_balance = value + unit * 4;
@@ -6119,12 +6119,12 @@ fn proportional_ledger_slash_works() {
         value - value_slash
     };
     assert_eq!(ledger.active, unit_slashed);
-    assert_eq!(ledger.unlocking, vec![c(5, value_slashed)]);
-    assert_eq!(ledger.total, value_slashed);
+    assert_eq!(ledger.unlocking, vec![c(5, value_slashed), c(7, 32)]);
+    assert_eq!(ledger.total, value_slashed + 32);
     assert_eq!(LedgerSlashPerEra::get().0, 0);
     assert_eq!(
         LedgerSlashPerEra::get().1,
-        BTreeMap::from([(4, 0), (5, value_slashed), (6, 0), (7, 0)])
+        BTreeMap::from([(4, 0), (5, value_slashed), (6, 0), (7, 32)])
     );
 }