Typo fixes and updates to block-time guide

guides/block-times.md

@@ -4,7 +4,7 @@ If you have gone through both the [GM world](./gm-world) and the
 [Full and sequencer node rollup setup](./full-and-sequencer-node)
 already, you're now ready to experiment with faster block times.
 
-In your `gmd start [args...]` command, you will need to add a flag
+In your `rollkit start [args...]` command, you will need to add a flag
 and then the argument for block time.
 
 The flag is:
@@ -19,8 +19,8 @@ Here is an example:
 
 ```bash
 # start the chain
-gmd start [existing flags...] // [!code --]
-gmd start [existing flags...] --rollkit.block_time 1s // [!code ++]
+rollkit start [existing flags...] // [!code --]
+rollkit start [existing flags...] --rollkit.block_time 1s // [!code ++]
 ```
 
 In the above example, we've changed it to one second blocks.
@@ -33,5 +33,5 @@ Alternatively, you could slow your rollup down to 30 seconds:
 Or speed it up even more, to sub-second block times (100 milliseconds):
 
 ```bash
---rollkit.block_time 0.1ms
+--rollkit.block_time 100ms
 ```