clarify mtmd_get_output_embd

Author: ngxson

tools/mtmd/mtmd.h

@@ -203,6 +203,8 @@ MTMD_API int32_t mtmd_encode_chunk(mtmd_context * ctx,
                                    const mtmd_input_chunk * chunk);
 
 // get output embeddings from the last encode pass
+// the reading size (in bytes) is equal to:
+// llama_model_n_embd(model) * mtmd_input_chunk_get_n_tokens(chunk) * sizeof(float)
 MTMD_API float * mtmd_get_output_embd(mtmd_context * ctx);
 
 /////////////////////////////////////////