tests/FILEFORMAT.md: clarify %hex[] formatting

Closes #17332

diff --git a/tests/FILEFORMAT.md b/tests/FILEFORMAT.md
index 263ce7f067bf63c4b7e799d9e409755078f1f1ef..0a0aee0fec85e54562c33dd11da8161ed1e561df 100644 (file)
--- a/tests/FILEFORMAT.md
+++ b/tests/FILEFORMAT.md
@@ -55,9 +55,11 @@ To insert a sequence of bytes from a hex encoded string, use this syntax:
 
     %hex[ %XX-encoded data to decode ]hex%
 
+Other bytes within the brackets that not percent encoded are inserted as-is.
+
 For example, to insert the binary octets 0, 1 and 255 into the test file:
 
-    %hex[ %00%01%FF ]hex%
+    %hex[%00%01%FF]hex%
 
 ## Repeat content