How in a p:dataTable does the filter event update a field outside the grid (such as a footer or backingBean variable)?

Question

Good afternoon. I'm having difficulty in JSF with PrimeFaces. In a grid, which brings a table. I created a filter, in the header, in the "Phase Type" column. In the BackingBean, it executes the "onFilter" event, and recalculates the cadProdutoBean.totalTempo property, it adds the total of the column according to the filter. I did tests in the console and the recalculation in cadProdutoBean.totalTempo works. However, it does not display the new value of cadProdutoBean.totalTempo on the screen. Does anyone know how to give me a tip on how to bring the new value of cadProdutoBean.totalTempo?

Obs.: I use: PrimeFaces 6, javax.faces 2.2.10

CadProduto.xhtml

<h:form id="frmSeqOper" >
    ...
    <p:dataTable id="seqTable" value="#{cadProdutoBean.produto.produtoSeqOpera}" 
                var="seq"
                emptyMessage="Nenhuma sequencia adicionada."
                reflow="true"
                style="margin-top: 10px" 
                editable="true" filterEvent="keyup">
                
    ...
                           <p:column headerText="Tipo Fase" filterBy="#{seq.seqOpera.custoTipoFase.nome}" filterMatchMode="contains" >
                               <p:cellEditor>
                                   <f:facet name="output"><h:outputText value="#{seq.seqOpera.custoTipoFase.nome}" /></f:facet>
                                   <f:facet name="input"><p:inputText disabled="true" id="tipoFaseInput" 
                                                value="#{seq.seqOpera.custoTipoFase.nome}" style="width:100%"/>
                                    </f:facet>
                               </p:cellEditor>
                           </p:column>  
    ...
                        
    <p:columnGroup type="footer" id="totalFooter">
            <p:row>                     
                <p:column colspan="6" style="text-align:left" footerText="Total:" />
                                    <p:column footerText="#{cadProdutoBean.totalTempo}" id="totalTempo" />
                                    <p:column colspan="1" style="text-align:left" footerText="" />
                                    <p:column colspan="1" style="text-align:left" footerText="" />
                                    <p:column colspan="1" style="text-align:left" footerText="" />
            </p:row>
    </p:columnGroup>                                             
                         <p:ajax event="filter" listener="#{cadProdutoBean.onFilter}" update="totalTempo" />
</p:dataTable>
                
                    <h:panelGroup>
                        <h:outputLabel value="Total Tempo:" />
                        <h:outputText value="#{cadProdutoBean.totalTempo}" id="ptotaltempo"  />
                    </h:panelGroup>
                
</h:form>

CadProdutoBean.java

public void onFilter(AjaxBehaviorEvent event) {