diff --git a/docs/part/trackable.md b/docs/part/trackable.md
index 1e0f231..5d4d42f 100644
--- a/docs/part/trackable.md
+++ b/docs/part/trackable.md
@@ -23,7 +23,7 @@ For faster input there are several ways to define the wanted serial numbers(SN):
 | , | `1,3,5` | `[1, 3, 5]` | list of SNs |
 | - | `1-5` | `[1, 2, 3, 4, 5]` | strech of SN |
 | `<start>`+ | `4+` (with 3 numbers needed) | `[4, 5, 6]` | all needed SNs from `<start>` |
-| `<start>`+<lenght> | `2+2` | `[2, 3, 4]` | `<length>` SNs added to `<start>` |
+| `<start>`+<length> | `2+2` | `[2, 3, 4]` | `<length>` SNs added to `<start>` |
 
 These rules can be mix-and-matched with whitespaces or commas separating them.  
 For example: