jqGrid width subgrid pager exceeds main grid width - jqgrid

Question

I hope my title is comprehensive !
I am developing my own personal account with one main grid and one grid as subgrid.
The trouble is that main grid pager is displayed fine, but subgrid pager exceeds the width of grid, such as below :
I don't understand what is wrong.
Here is the subgrid code :
subGridRowExpanded: function(subgrid_id, row_id) {
var rowdata = $("#jqGrid").jqGrid('getRowData',row_id),
catg=rowdata.cg_id,
subgrid_table_id = subgrid_id+"_t",
pager_id = "p_"+subgrid_table_id;
$("#"+subgrid_id).closest("td").attr("colspan", 20)
.css({
borderRight:0,
borderLeft:0,
padding:0
})
.parent().find('td:eq(0)')
.addClass('ui-widget-content')
.addClass('ui-state-highlight')
.css({
borderLeft:0,
borderTop:0
});
$("#"+subgrid_id).html("<table id='"+subgrid_table_id+"' class='scroll'></table><div id='"+pager_id+"'></div>");
$("#"+subgrid_table_id).jqGrid({
url:"subc.php?rowid="+row_id+"&catg="+catg,
idPrefix:'s_'+row_id+'_',
datatype: "json",
colNames: ["ID","id_cp","Nom du poste"],
colModel:[
{
name:"su_id",
hidden:true
},
{
name:"id_cg",
hidden:true
},
{
name:"su_name"
}
],
caption:"Liste des postes budgétaires",
hidegrid: false,
gridview: true,
autowidth:true,
shrinkToFit:false,
viewrecords: true,
recordtext: "Postes {0} - {1} of {2}",
emptyrecords: "Aucun poste à afficher",
rownumbers:true,
rownumWidth:40,
altRows:false,
height:"auto",
maxHeight: (23*15),
rowNum: 20,
pager: pager_id,
loadComplete: function(){
$("#gview_"+subgrid_table_id+" .ui-jqgrid-titlebar .ui-jqgrid-title").css({color:'#875', fontWeight:'bold', fontSize:'1.2rem', lineHeight:'1.3rem',marginLeft:'10px'});
}
});
$("#"+subgrid_table_id).jqGrid('navGrid',"#"+pager_id,{search:false});
}
I'm sure that's a newbie mistake, and I hope somebody could help me.
Many thanks in advance
Cheers
JiheL