2816143 - sp_sysmon "sample interval"parameter less than "sample interval" in the output - How is this possible?

A simple sysmon running for 5 minutes is showing a sample time of 9 minutes or more.  For example:

sp_sysmon "00:05:00"
go

But the results show:

Server Version: Adaptive Server Enterprise/16.0 SP03 PL04/EBF 27872 SMP/P/x86_64/SLES 11.1/ase160sp03pl04x/3394/64-bit/FBO/Sun May 6 21:48:04 2018
Run Date: Jul 10, 20XX
Sampling Started at: Jul 10, 20XX 03:31:12
Sampling Ended at: Jul 10, 20XX 03:40:30
Sample Interval: 00:09:18
Sample Mode: No Clear
Counters Last Cleared: Jul 10, 20XX 03:10:13
Server Name: MYSERVER

How can the Sample Interval in the results, be longer than the Sample Interval given in the execution parameters?

SAP Adaptive Server Enterprise

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