description.md in trackler-2.0.6.28

- old
+ new

@@ -11,5 +11,8 @@
 the compressed data, which makes it a lossless data compression.
 
 ```
 "AABCCCDEEEE"  ->  "2AB3CD4E"  ->  "AABCCCDEEEE"
 ```
+
+For simplicity, you can assume that the unencoded string will only contain
+the letters A through Z.
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