diff --git a/doc/disk-victor9k.md b/doc/disk-victor9k.md
index 01f49699..9bba7dc5 100644
--- a/doc/disk-victor9k.md
+++ b/doc/disk-victor9k.md
@@ -16,8 +16,8 @@ the speed zone allocation on head 1 differ from head 0...
 | 1    | 4-15          | 0-7           | 18      | 224.5                |
 | 2    | 16-26         | 8-18          | 17      | 212.2                |
 | 3    | 27-37         | 19-29         | 16      | 199.9                |
-| 4    | 38-48         | 30-40         | 15      | 187.6                |
-| 5    | 49-59         | 41-51         | 14      | 175.3                |
+| 4    | 38-47\*       | 30-39\*       | 15      | 187.6                |
+| 5    | 48-59         | 40-51         | 14      | 175.3                |
 | 6    | 60-70         | 52-62         | 13      | 163.0                |
 | 7    | 71-79         | 63-74         | 12      | 149.6                |
 | 8    |               | 75-79         | 11      | 144.0                |
@@ -26,8 +26,13 @@ the speed zone allocation on head 1 differ from head 0...
 FluxEngine, the disk always spins at 360 rpm, which corresponds to a rotational
 period of 166 ms.)
 
-FluxEngine can read and write the single-sided variant of these. (Double-sided
-will be trivial to do, it's just not done yet.)
+\*The Victor 9000 Hardware Reference Manual has a bug in the documentation 
+and lists Zone 4 as ending with track 48 on head 0 and track 40 on head 1. 
+The above table matches observed data on various disks and the assembly 
+code in the boot loader, which ends Zone 4 with track 47 on head 0 
+and track 39 on Head 1.
+
+FluxEngine can read and write both the single-sided and double-sided variants. 
 
 Reading discs
 -------------
@@ -35,10 +40,14 @@ Reading discs
 Just do:
 
 ```
-fluxengine read victor9k-ss
+fluxengine read <format>
+
 ```
 
-You should end up with an `victor9k.img` which is 627200 bytes long.
+...where `<format>` can be `victor9k_ss` or `victor9k_ds`. 
+
+For `victor9k_ss` you should end up with an `victor9k.img` which is 627200 bytes long. 
+For `victor9k_ds` you should end up with an `victor9k.img` which is 1224192 bytes long.
 
 **Big warning!** The image is triangular, where each track occupies a different
 amount of space. Victor disk images are complicated due to the way the tracks
@@ -50,7 +59,7 @@ Writing discs
 Just do:
 
 ```
-fluxengine read victor9k-ss -i victor9k.img
+fluxengine read victor9k_ss -i victor9k.img
 ```
 
 **Big warning!** This uses the same triangular disk image that reading uses.