diff --git a/tsdb/docs/format/chunks.md b/tsdb/docs/format/chunks.md
index 596270ce59..a604c9ea55 100644
--- a/tsdb/docs/format/chunks.md
+++ b/tsdb/docs/format/chunks.md
@@ -35,7 +35,7 @@ in-file offset (lower 4 bytes) and segment sequence number (upper 4 bytes).
 
 Notes:
 
-* `len`: Chunk size in bytes. 1 to 10 bytes long using the [`<uvarint>` encoding](https://go.dev/src/encoding/binary/varint.go).
+* `len`: Chunk size in bytes. 1 to 5 bytes long using the [`<uvarint>` encoding](https://go.dev/src/encoding/binary/varint.go).
 * `encoding`: Currently either `XOR`, `histogram`, or `floathistogram`, see [code for numerical values](https://github.com/prometheus/prometheus/blob/02d0de9987ad99dee5de21853715954fadb3239f/tsdb/chunkenc/chunk.go#L28-L47).
 * `data`: See below for each encoding.
 * `checksum`: Checksum of `encoding` and `data`. It's a [cyclic redundancy check](https://en.wikipedia.org/wiki/Cyclic_redundancy_check) with the Castagnoli polynomial, serialised as an unsigned 32 bits big endian number. Can be referred as a `CRC-32C`.