diff --git a/store.md b/store.md
index 70892a3..ab8d6d8 100644
--- a/store.md
+++ b/store.md
@@ -37,5 +37,8 @@ An index is a dict with a string as key and a list of objects as value. The dict
 type may be a class or a string containing the name of a class. The type should be a subclass of models.base.Base
 
 # file format
+Until specified otherwise, all numbers are stored low-endian 64bit unsigned.
+
 the file format is a header followed by a number of blocks. the size and number of blocks are dictated by the header.
 
+