Data set fails with one record

[spruce18b]

I want to calculate Poisson P(X) with lamda=2, x=1.  
Could someone please tell me why X has a probability of 0 instead of .1839?

data list / x 1-2.
variable labels x "P(x)".
begin data.
0
end data.
formats x (f4.0).
COMPUTE x=PDF.POISSON(2,1).
execute.
list.
execute.

[spruce18b]

Formats should have been (F6.4).