From phpBB Development Wiki
This file contains the configuration information for the style's templates
The file contains the following information for use within phpBB3
name = NameofStyle copyright = © 2007 Name of Creator version = 1.2.3
There is one directive, the template bitfield, which must be present, but is not fully used in phpBB3:
template_bitfield = lNg=
Beginning with phpBB 3.0.3, there will be an additional option to make a template dependent upon another.
inherit_from = prosilver
The above would cause the template being installed to fall back to prosilver if a template file should be missing from the template.
Version numbers usually follow the typical Version Numbering guidelines.