why is parallel rspec showing a different coverage percentage and missed resources compared to rspec?

Sysctl[net.ipv6.conf.all.accept_redirects]
  Sysctl[net.ipv6.conf.all.disable_ipv6]
  Sysctl[net.ipv6.conf.default.accept_ra]
  Sysctl[net.ipv6.conf.default.accept_redirects]
  Sysctl[net.ipv6.conf.default.disable_ipv6]
  Sysctl[net.ipv6.conf.lo.disable_ipv6]
  Sysctl[vm.min_free_kbytes]
  Sysctl[vm.swappiness]
  Systemd::Unit_file[puppet_runner.service]
  Users[application]
  Users[global]
F

Failures:

1) Code coverage. Must be at least 95% of code coverage Failure/Error: RSpec::Puppet::Coverage.report!(95)

   expected: >= 95.0
        got:    79.01
 # /usr/local/bundle/gems/rspec-puppet-2.6.11/lib/rspec-puppet/coverage.rb:104:in `block in coverage_test'
 # /usr/local/bundle/gems/rspec-puppet-2.6.11/lib/rspec-puppet/coverage.rb:106:in `coverage_test'
 # /usr/local/bundle/gems/rspec-puppet-2.6.11/lib/rspec-puppet/coverage.rb:95:in `report!'
 # ./spec/spec_helper.rb:22:in `block (2 levels) in <top (required)>'

Finished in 42.12 seconds (files took 2.11 seconds to load) 995 examples, 1 failure

Failed examples:

rspec # Code coverage. Must be at least 95% of code coverage

2292 examples, 2 failures

....................................................................

Total resources:   1512
Touched resources: 1479
Resource coverage: 97.82%
Untouched resources:

  Apt::Source[archive.ubuntu.com-lsbdistcodename-backports]
  Apt::Source[archive.ubuntu.com-lsbdistcodename-security]
  Apt::Source[archive.ubuntu.com-lsbdistcodename-updates]
  Apt::Source[archive.ubuntu.com-lsbdistcodename]
  Apt::Source[postgresql]

Finished in 1 minute 25.3 seconds (files took 1.43 seconds to load)
2292 examples, 0 failures