A microstate names one exact arrangement, while a macrostate groups arrangements that share the same counted feature. Here the feature is heads count, so the four listed arrangements collapse into buckets with different multiplicities. The probabilities are exact count ratios for this toy ledger; a real ensemble would still need an honest statement of how the states were prepared and counted.
A macrostate probability begins as a finite count ledger. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
A macrostate is a counted bucket
The checked ledger groups four microstates into heads-count buckets.
Ω=4,P(H=1)=42=21
The probability is not a caption
The diagram's probability label is derived from the same count ledger.