Understanding the x18 instruction jump table

I was looking at the instruction decoding code for 
the x18 simulator and I noticed something a little 
odd.

: inst ( n ) 1 slot +! 1f and jump jmp jmp call call
jz jz jns jns @b @+ n @a !b !+ nul !a -x 2*x 2/x +*
orx andx nul +x r@ a@ t@ s@ r! a!x nul t!

Why are the opcodes jmp, call and jns repeated?

Side note, I'm working on a c18 disassembler.  It's
really simple.  It just shows the opcode of the
last executed instruction on the screen below
the data stack.  In fact, I've got it "working"
but I'm not confident in my results due to
my uncertainty about the duplicated opcodes.

Regards,

John M. Drake

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