How to Read the Signs

Each sign represents an intersection with three directions.

Dutch Flat Trail .7 ^
Canada Trail .3 <-
Heron Trail .3 ->

This means that if one walks to the right they will be walking on Heron Trail. In 0.3 units, another intersection will be reached. Walk to the left will be on Canada trail and in 0.3 units an intersection will be reached. Walk straight and in 0.7 units an intersection will be reached.

The Confusion

One sign (A) has the following instructions:

Dutch Flat Trail .1 ->
Dutch Flat Trail .7 ->

Walking right, in 0.1 units an intersection will be reached. The shortest path to the entrance is 0.7 units.

The missing piece of information is which of the two those point to.

Sum it Up

The entrance is D because it is the only one at the head of three paths.

The letters in the squares are the sign posts. The letters in the circles are the trail names.

The longest non-overlapping path from the entrance is:
D -> B (0.7)
B -> E (0.3)
E -> A (0.7)
A -> F (0.6)
F -> C (0.3)
Total = 2.6 units