The data chunk sizes add to the decoded body length.
Two data chunks add up
The first data chunk contributes 2 bytes.
first chunk bytes=2
The second data chunk adds one more byte
The second data chunk contributes 1 byte.
second chunk bytes=1
The decoded body length is counted
The two data chunk sizes add to 3 body bytes.
Summary
Chunked transfer counts body bytes from the chunk size lines.
chunk sizes checked