Fix #858, clarification on non-scalable layer config

index.bs

@@ -1920,6 +1920,7 @@ Common restrictions on the [=IA Sequence=] for all profiles specified in this ve
 NOTE: This behavior is to allow future versions of this specification to define new profiles that support a number of audio elements and/or a number of sub-mixes greater than those recommended in this profile, while still permitting streams compliant with these new profiles to be processed by parsers compliant with the profiles defined in this version of the specification.
 
 - When [=num_layers=] = 1, [=DemixingParamDefinition()=] for demixing MAY be present in the [=Audio Element OBU=] and IA decoders MAY use [=demixing_info_parameter_data=] or [=default_demixing_info_parameter_data=] for (dynamic) down-mixing.
+	- Both [=output_gain_is_present_flag=] and [=recon_gain_is_present_flag=] SHALL be set to 0.
 - The limit on the number of channels, which profiles MAY define, applies to the sum of channels across all [=Audio Element=]s in a [=Mix Presentation=] before mixing.
 - There MAY be [=Temporal Delimiter OBU=]s present. If present, the first OBU of every [=Temporal Unit=] SHALL be the [=Temporal Delimiter OBU=].
 - There SHALL be at least one [=Mix Presentation OBU=] that complies with the conformance points of the [=primary_profile=] set in the [=IA Sequence=].