Is it correct that ADF always uses the whole range instead of the current sample?

? adf 8 log(salarios) --ct

Augmented Dickey-Fuller test for l_salarios
including 8 lags of (1-L)l_salarios
sample size 19
unit-root null hypothesis: a = 1

   with constant and trend 
   model: (1-L)y = b0 + b1*t + (a-1)*y(-1) + ... + e
   1st-order autocorrelation coeff. for e: 0,179
   lagged differences: F(8, 8) = 4,559 [0,0231]
   estimated value of (a - 1): -0,979101
   test statistic: tau_ct(1) = -5,3047
   asymptotic p-value 4,382e-005

? smpl
Full data range: 2002:1 - 2008:4 (n = 28)

? smpl
Full data range: 2002:1 - 2008:4 (n = 28)
Current sample: 2004:1 - 2008:4 (n = 20)

? adf 8 log(salarios) --ct

Augmented Dickey-Fuller test for l_salarios
including 8 lags of (1-L)l_salarios
sample size 19
unit-root null hypothesis: a = 1

   with constant and trend 
   model: (1-L)y = b0 + b1*t + (a-1)*y(-1) + ... + e
   1st-order autocorrelation coeff. for e: 0,179
   lagged differences: F(8, 8) = 4,559 [0,0231]
   estimated value of (a - 1): -0,979101
   test statistic: tau_ct(1) = -5,3047
   asymptotic p-value 4,382e-005


Thanks!