RFR: 8321292: SerialGC: NewSize vs InitialHeapSize check has an off-by-one error

[Thomas Schatzl]

Hi all,

  please review this change to the warning message to improve the understanding why the change is needed.
I tried to make the message similar to surrounding ones, adding actual values.

Testing: local compilation, manual testing

Thanks,
  Thomas

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Commit messages:
 - 8321292

Changes: https://git.openjdk.org/jdk/pull/19384/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19384&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8321292
  Stats: 5 lines in 1 file changed: 3 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/19384.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19384/head:pull/19384

PR: https://git.openjdk.org/jdk/pull/19384