Question about the format comments in Add and Put methods of Memtable.

Hello, Recently I am learning leveldb by reading its source code. When I saw this function fallow:

~~~c++
void MemTable::Add(SequenceNumber s, ValueType type, const Slice& key,
const Slice& value) {
// Format of an entry is concatenation of:
// key_size : varint32 of internal_key.size()
// key bytes : char[internal_key.size()]
// tag : uint64((sequence << 8) | type)
// value_size : varint32 of value.size()
// value bytes : char[value.size()]

~~~

I have a question about this comments of key bytes format. Shouldn't it' s size be the `user_key` 's size which equal to `internal_key.size() - 8`? Why this comment say its size is the size of the` internal_key`?