rs.printSecondaryReplicationInfo() shows negative value on primary

Installed MongoDB 6.0 and using mongosh, rs.printSecondaryReplicationInfo() shows negative value on primary. The manual indicates that it would show negative value if rs.printSecondaryReplicationInfo() executed on secondary but not primary.

USWest [direct: primary] test> rs.printSecondaryReplicationInfo()
source: mon-sec-useast.xxx.com:27018
{
syncedTo: ‘Fri Aug 30 2024 17:33:37 GMT+0000 (Coordinated Universal Time)’,
replLag: '-2 secs (0 hrs) behind the primary ’
}

source: mon-sec-usnw-b.xxx.com:27018
{
syncedTo: ‘Fri Aug 30 2024 17:33:38 GMT+0000 (Coordinated Universal Time)’,
replLag: '-1 secs (0 hrs) behind the primary ’
}

source: monsec-west-or.xxx.com:27018
{
syncedTo: ‘Fri Aug 30 2024 17:33:38 GMT+0000 (Coordinated Universal Time)’,
replLag: '-1 secs (0 hrs) behind the primary ’
}