I'm assuming the 'circular park' is aproximately a circlein that case, 'the way around' would be the circumference'the way across' is the diameter
we know of a relationship between circumference and diameer in the folowing formula: C=πd where C=circumference, d=diameter and π=pi, the irrational number
so if we know C, then d=C/πand π≈3.14159265
so since C=62.8, d=62.8/π≈20 meters
it's about 20meters across the park