<apex:pageBlockTable value="{!oldSubscriptionAndAsset}" var="assetAndSubs" id="subscribedAsset" rendered="{!isRenewal}">
     <apex:column styleClass="order-product-column order-product-top-level-value" headerClass="order-product-header">
           <apex:facet name="header">Asset</apex:facet>
           <apex:outputText value="{!assetAndSubs.SBQQ__Asset__r.Name}"/>
     </apex:column>
</apex:pageBlockTable>

oldSubscriptionAndAsset = [SELECT Id, SBQQ__Product__r.Name, SBQQ__Quantity__c,(SELECT Id, SBQQ__Asset__r.Name, SBQQ__Asset__r.SerialNumber, SBQQ__Asset__r.Is_Selected_For_Renewal__c  FROM SBQQ__SubscribedAssets__r) FROM SBQQ__Subscription__c];