A finite sample set can be exactly ambiguous until denser samples are taken. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Sparse samples can leave two patterns ambiguous
Sampling positions 0, 2, 4, 6 gives the same output for both patterns, so ambiguous bit is 1.
(1,1,1,1)=(1,1,1,1)⇒1
Denser samples separate the patterns
Sampling all 8 positions gives different dense outputs, so separated bit is 1.