Welcome to the PICAXE forum.
It's not an error as such just a difference in how things work and are implemented. The Programming Editor / PICAXE does not support "WAIT <variable>", the WAIT 1 command is equivalent to PAUSE 1000 so you can do the following -
For b13 = 0 To b0
Pause 1000
Next
Note that will use an additional variable, 'b13'. When programming using the Flowchart tools this is hidden from you.