file-format.md: list full block overhead

For large files, the overhead will be 0.78125 %.
2018-07-15 11:24:54 +02:00 · 2018-07-15 11:24:54 +02:00 · 2ed3f128dd
commit 2ed3f128dd
parent 95b93db35f
1 changed files with 1 additions and 0 deletions
--- a/Documentation/file-format.md
+++ b/Documentation/file-format.md
@ -12,6 +12,7 @@ Data block
 	1-4096 bytes encrypted data
 	16 bytes GHASH

+Full block overhead = 32/4096 = 1/128 = 0.78125 %

 Example: 1-byte file
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