checkboxlist doesnt chage size when It populates

I have a problema, I have a checkbox in a form, and It doesnt chage its size when its populating with data

this is my code:

$competencia_estado_id=array_unique(ArrayHelper::getColumn(\app\models\CompetenciaEstado::findAll([‘estado_id’=>$this->estado_id,‘activo’=>1]),‘id’));

$disciplina_id=array_unique(ArrayHelper::getColumn(\app\models\Individual::find()->where([‘atleta_id’=>$post[‘atleta_id’]])->andWhere([‘in’,‘competencia_estado_id’,$competencia_estado_id])->all(),‘disciplina_id’));

$html=Html::label($disciplinas[0]->elemento->nombre,array(‘class’=>‘control-label’));

$html.=Html::checkboxList(‘ultima’, $disciplina_id, ArrayHelper::map($disciplinas, ‘id’, ‘nombre’),array(‘class’=>‘form-control’));

$html.=’<br><div class=“form-group”>’.