what does the output mean?

[staabm]

when running a phpunit test-suite with this extension, I get a output like:

1. 11.635 (0.500) PHPStan\Analyser\AnalyserIntegrationTest::testBug11913
 2.  4.981 (0.500) PHPStan\Reflection\SignatureMap\SignatureMapParserTest::testParseAll with data set #0 (70400)
 3.  3.461 (0.500) PHPStan\Analyser\AnalyserIntegrationTest::testBug5081
 4.  2.388 (0.500) PHPStan\Analyser\AnalyserIntegrationTest::testBug11283
 5.  2.387 (0.500) PHPStan\Analyser\AnalyserIntegrationTest::testBug9690
 6.  2.145 (0.500) PHPStan\Rules\Methods\FinalPrivateMethodRuleConfigPhpTest::testRulePhpVersions
 7.  1.773 (0.500) PHPStan\Analyser\AnalyserIntegrationTest::testBug11297
 8.  1.484 (0.500) PHPStan\Analyser\AnalyserIntegrationTest::testBug10772
 9.  1.259 (0.500) PHPStan\Analyser\AnalyserIntegrationTest::testBug10538
10.  1.252 (0.500) PHPStan\Rules\Methods\ReturnTypeRuleTest::testBug8146bErrors

I wonder what the (0.500) number - which is repeated across the whole top 10 - is trying to tell me?