diff --git a/docs/embed-va.md b/docs/embed-va.md
index 4187a7e..da94d4c 100644
--- a/docs/embed-va.md
+++ b/docs/embed-va.md
@@ -6,16 +6,14 @@ description: Embed the Data Controller editor inside a SAS VA report as a data-d
 
 # Embedding inside SAS Visual Analytics
 
-Data Controller can be embedded inside a SAS Visual Analytics report as a **data-driven content** (DDC) object.  This unlocks scenarios where a user can safely modify the values in an underlying SAS table, and have the visualisation updated- all from inside the same report.
+Data Controller can be embedded inside a SAS Visual Analytics report as a **data-driven content** (DDC) object.  This unlocks scenarios where a user can safely modify the values in an underlying SAS table, and have the visualisation updated - all from inside the same report.
 
 ## URL
 
 Open the editor as a DDC by appending `?embed=va` to the editor route:
 
-```
-
-`https://yourserver/DC/#/editor/<library>/<table>?embed=va`
-
+```text
+https://yourserver/DC/#/editor/<library>/<table>?embed=va
 ```
 
 The `?embed=` parameter accepts three values:
@@ -46,11 +44,11 @@ VA pushes a JSON payload to the iframe via `window.postMessage` whenever the sel
 
 1. Resolves each VA `parameter` to a DC column by matching on column label.
 2. Builds a filter (using existing [Filter](/filter/) machinery) over the selected values.
-3. Hides any VA columns marked as `brush` so the grid stays focused on the user-editable columns (except primary key cols which are always shown)
+3. Hides any VA columns marked as `brush` so the grid stays focused on the user-editable columns (primary key columns are always shown).
 
 If VA sends an empty / unmatched message the editor falls back to the unfiltered view but stays in VA mode.
 
-More logic available in [`va-messaging.service.ts'](https://git.datacontroller.io/dc/dc/src/branch/main/client/src/app/services/va-messaging.service.ts).
+More logic available in [`va-messaging.service.ts`](https://git.datacontroller.io/dc/dc/src/branch/main/client/src/app/services/va-messaging.service.ts).
 
 ## Mapping parameters to columns
 
@@ -100,6 +98,8 @@ Each line names one cause, and the parameter it concerns is skipped rather than
 | `a range needs one value` | a `RANGE` mapping was sent several values - one `BETWEEN` carries one period |
 | `N of its M values was not a date` | part of a multi-value parameter could not be read as a date, so only the rest is applied |
 | `was ignored: it needs a "-"` / `is not a transform` | the entry itself is malformed |
+| `the VA parameter name is missing` | the entry starts with the `-`, so there is no parameter to map |
+| `already maps to <COLUMN>, and a parameter can filter only one column` | the same parameter is mapped twice; the first entry wins |
 
 The banner is shown to the report author, inside the report, because that is where the entry is edited: the only fix available from the editor is to change the `va_parmap` entries in the URL of the Data Controller object.