the number of MiniBatchSize always 1 even when i change it in minibatchqueue parameters ?

i follow the example in

Train Network with Multiple Outputs

https://www.mathworks.com/help/deeplearning/ug/train-network-with-multiple-outputs.html

but with color image as

 Name          Size                        Bytes  Class     Attributes

  XTrain      128x128x3x2016            792723456  double              

  Name              Size              Bytes  Class          Attributes

  yTrain1      1x2016             2230  categorical              

  Name              Size              Bytes  Class     Attributes

  yTrain2      1x2016            16128  double   

i define minibatchqueue as below:

mbq = minibatchqueue(dsTrain,...
    'MiniBatchSize',32,...
    'MiniBatchFcn', @preprocessDataJwan,...
    'MiniBatchFormat',{'SSCB','',''});

but minibatchqueue not deveded the to 32 Batch Size:

mbq = 

minibatchqueue with 3 outputs and properties:

Mini-batch creation:
MiniBatchSize: 1
PartialMiniBatch: 'return'
MiniBatchFcn: @preprocessDataJwan
DispatchInBackground: 0

Outputs:
OutputCast: {'single'  'single'  'single'}
OutputAsDlarray: [1 1 1]
MiniBatchFormat: {'SSCB'  ''  ''}
OutputEnvironment: {'auto'  'auto'  'auto'}

even i check output:

dlX,dlY1,dlY2] = next(mbq);
         size(dlX)
         size(dlY1)
         size(dlY2)

ans =

128 128 3 2016

ans =

2 2016

ans =

1 2016