The toy code saves one bit here, with clear limits on what that means.
Fixed names spend the same width
With four symbols, a fixed code would spend 2 bits on every symbol.
fixed width=2
The fixed length
The message has 6 symbols, so fixed names use 12 bits.
The Huffman length
The Huffman message uses 11 bits: one bit shorter for this tiny message.
12 minus 11=1
What this toy leaves out
NOTE: toy static prefix code only. This is not adaptive compression, not a file format, not an entropy optimality proof, and not encryption.
toy static prefix code only
Summary
Huffman coding gives common symbols shorter names. In this pinned example, ABACAD uses 11 Huffman bits instead of 12 fixed bits.