spec(BACK-8009): precise slices specification

specs/erc-7730.md

@@ -195,7 +195,7 @@ This specification uses a limited [json path](https://www.rfc-editor.org/rfc/rfc
 Limitation to the json path specification are the following:
 * Paths MUST use the dot notation, including for slice and array selectors (i.e. an element of an array should be selected through `array_name.[index]`) 
 * Only name, index and slices selectors are supported.
-* Slices selectors MUST NOT contain the optional step.
+* Slices selectors MUST NOT contain the optional step. Start index is inclusive, end index is exclusive. Start or end index can be omitted to indicate the beginning or end of the array.
 
 In addition, additional *roots* are introduced to support description of paths over multiple files in a single common notation. The root node identifier indicates which document or data location this path references, according to the following table:
 
@@ -214,8 +214,8 @@ For paths referring to structured data fields, if a field has a variable length
 References to values in the serialized structured data
 * `#.params.amountIn` or `params.amountIn` refers to parameter `amountIn` in top-level structure `params` as defined in the ABI
 * `#.data.path.[0].path.[-1].to` or `data.path.[0].path.[-1].to` refers to the field `to` taken from last member of `path` array, itself taken from first member of enclosing `path` array, itself part of top level `data` structure.
-* `#.params.path.[0:19]` refers to the first 20 bytes of the `path` byte array
-* `#.params.path.[-20:-1]` refers to the last 20 bytes of the `path` byte array
+* `#.params.path.[:20]` or `#.params.path.[0:20]` refers to the first 20 bytes of the `path` byte array
+* `#.params.path.[-20:]` refers to the last 20 bytes of the `path` byte array
 * `#.details.[]` refers to the array with the Permit Details of a PermitBatch message
 
 References to values in the format specification file
@@ -819,7 +819,7 @@ A slice on an array type means that the associated [field format specification](
                         "label": "Maximum Amount to Send",
                         "format": "tokenAmount",
                         "params": {
-                            "tokenPath": "params.path.[0:19]"
+                            "tokenPath": "params.path.[0:20]"
                         }
                     }
                 ]