The first calculation is an integer pair-count table. Frequencies weight each adjacent occurrence, so the displayed corpus determines every count.
highlighted = computed this step
Counting adjacent pairs
A pair count is the sum over words of frequency times adjacent occurrences. Every count is an integer because the corpus frequencies and occurrences are integers.
pair count=∑freq⋅adjacent occurrences
Round one counts
From the shown corpus, (h,u) has count 3, (u,g) has count 5, and (p,u) has count 2.
(h,u)=3,(u,g)=5,(p,u)=2
Summary
The largest count is attached to (u,g). The next step applies the deterministic merge rule to that exact maximum.