The WORKDAY function returns the first weekday date that is the
specified number of days from your start date. When your start date is
in the middle of the week, your formula returns the next day- when that
day is a weekday. The August and October dates are on a weekend or a
Friday, so they don't return the next day, they return the next soonest
weekday- that's what the WORKDAY function does.

If you would like to return the next day's date, regardless of
weekday/weekend, you can simply use
=A5+1
for example.

What are you trying to do? It may be a matter of using another formula.