docs: fix the numbering in "Converting an existing Mac checkout" section

docs/ios_build_instructions.md

 # iOS Build Instructions
 
 **Note:** Upstreaming of iOS code is still a work in progress. In particular,
 note that **it is not currently possible to build an actual Chromium app.**
 Currently, the buildable binaries are ios\_web\_shell (a minimal wrapper around
 the web layer), and various unit tests.
 
 ## Prerequisites
 
 *   A Mac with a version of OS X capable of running the latest version
@@ skipping 80 matching lines @@
 ```
 
 ## Converting an existing Mac checkout into an iOS checkout
 
 If you want to convert your Mac checkout into an iOS checkout, follow the steps
 below:
 
 1.  Add `target_os = [ "ios" ]` to the bottom of your `chromium/.gclient`
 file.
 
-1.  Make sure you have the following in your `chromium/chromium.gyp_env`
+2.  Make sure you have the following in your `chromium/chromium.gyp_env`
 file (removing the `chromium_ios_signing=0` if you want to make
 developer-signed builds):
 
 ```json
 {
   "GYP_DEFINES" : "OS=ios chromium_ios_signing=0",
   "GYP_GENERATORS" : "ninja,xcode-ninja",
 }
 ```
 
-1.  Make sure to sync again to fetch the iOS specific dependencies and
+3.  Make sure to sync again to fetch the iOS specific dependencies and
 regenerate build rules using:
 
 ```shell
 gclient sync
 ```
 
 ## Troubleshooting
 
 If your build fails, check the iOS columns of [the Mac
 waterfall](http://build.chromium.org/p/chromium.mac/console) (the last two) to
 see if the bots are green. In general they should be, since failures on those
 bots will close the tree.