Exactly as described, this is the ID of a specific EMIX sequence, from the cienaCesBenchmarkEmixSequenceTable, used instead of the plain frame-size list, but only when the Y1564 test is selected for this profile. Because this field is silently ignored unless the Y1564 test is enabled, an operator who carefully configures a specific EMIX sequence here but forgets to also enable the Y1564 test on this same profile would see the test still run using the plain frame-size list instead, a common source of confusion when reviewing test configuration. For example, a profile with an EMIX sequence set to a custom voice-mix pattern but Y1564Test left false would run its throughput and frameloss legs using the SetFrameSizeList instead, silently ignoring the configured EMIX sequence.