If I run the example here:  https://www.mongodb.com/docs/manual/reference/operator/aggregation/lastN/#computing-n-based-on-the-group-key-for–group, I get the following results:

{ "_id" : \{ "gameId" : "G1" }

, "gamescores" : [ 33, 99, 1 ] }

{ "_id" : \{ "gameId" : "G2" }

, "gamescores" : [ 80 ] }

But the docs show, correctly, that for G2 there should be only a 10 there.  I'm literally using the 'copy' action on the page and pasting in to my local shell and getting those results.  Am I tripping or is there a bug here? 

server build info as follows:

db.serverBuildInfo()
{
        "version" : "6.0.1",
        "gitVersion" : "32f0f9c88dc44a2c8073a5bd47cf779d4bfdee6b",
        "targetMinOS" : "Windows 7/Windows Server 2008 R2",
        "modules" : [ ],
        "allocator" : "tcmalloc",
        "javascriptEngine" : "mozjs",
        "sysInfo" : "deprecated",
        "versionArray" : [
                6,
                0,
                1,
                0
        ],
        "openssl" :

{                 "running" : "Windows SChannel"         }

,
        "buildEnvironment" :

{                 "distmod" : "windows",                 "distarch" : "x86_64",                 "cc" : "cl: Microsoft (R) C/C++ Optimizing Compiler Version 19.31.31107 for x64",                 "ccflags" : "/nologo /WX /FImongo/platform/basic.h /EHsc /W3 /wd4068 /wd4244 /wd4267 /wd4290 /wd4351 /wd4355 /wd4373 /wd4800 /wd4251 /wd4291 /we4013 /we4099 /we4930 /errorReport:none /MD /O2 /Oy- /bigobj /utf-8 /permissive- /Zc:__cplusplus /Zc:sizedDealloc /volatile:iso /diagnostics:caret /std:c++17 /Gw /Gy /Zc:inline",                 "cxx" : "cl: Microsoft (R) C/C++ Optimizing Compiler Version 19.31.31107 for x64",                 "cxxflags" : "/TP",                 "linkflags" : "/nologo /DEBUG /INCREMENTAL:NO /LARGEADDRESSAWARE /OPT:REF",                 "target_arch" : "x86_64",                 "target_os" : "windows",                 "cppdefines" : "SAFEINT_USE_INTRINSICS 0 PCRE_STATIC NDEBUG BOOST_ALL_NO_LIB _UNICODE UNICODE _SILENCE_CXX17_ALLOCATOR_VOID_DEPRECATION_WARNING _SILENCE_CXX17_OLD_ALLOCATOR_MEMBERS_DEPRECATION_WARNING _SILENCE_CXX17_CODECVT_HEADER_DEPRECATION_WARNING _SILENCE_ALL_CXX20_DEPRECATION_WARNINGS _CONSOLE _CRT_SECURE_NO_WARNINGS _ENABLE_EXTENDED_ALIGNED_STORAGE _SCL_SECURE_NO_WARNINGS _WIN32_WINNT 0x0A00 BOOST_USE_WINAPI_VERSION 0x0A00 NTDDI_VERSION 0x0A000000 BOOST_THREAD_VERSION 5 BOOST_THREAD_USES_DATETIME BOOST_SYSTEM_NO_DEPRECATED BOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS BOOST_ENABLE_ASSERT_DEBUG_HANDLER BOOST_LOG_NO_SHORTHAND_NAMES BOOST_LOG_USE_NATIVE_SYSLOG BOOST_LOG_WITHOUT_THREAD_ATTR ABSL_FORCE_ALIGNED_ACCESS"         }

,
        "bits" : 64,
        "debug" : false,
        "maxBsonObjectSize" : 16777216,
        "storageEngines" : [
                "devnull",
                "ephemeralForTest",
                "wiredTiger"
        ],
        "ok" : 1
}