Вы должны преобразовать string
значение в number
Заменить
var nameMatchT = Math.round(splitvalue[i]);
на
var nameMatchT = Math.round(Number(splitvalue[0]));
$("#NameMatchSummary").each(function() {
var namematch = $(this).find('.divNameMatch').length;
for (var o = 1; o <= namematch; o++) {debugger;
var namevalue = $('#spnNameMatch' + o).text();
var splitvalue = namevalue.split('%');
//var nameMatchT = Math.round(splitvalue);
var nameMatchT = Math.round(Number(splitvalue[0]));
//alert(nameMatchT);
$('#spnNameMatch' + o).text(nameMatchT + "%");
}
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div id="NameMatchSummary" class="pad1x flex-col-xs-3 flex-col-sm-6 DataSourceEnqInfo">
<div id="divNameMatch" class="divNameMatch flex-row_left divEnqInfo">
<div class="pad1x NameMatchiv">
<span class="labelValue" name="spnNameMatch" id="spnNameMatch1">0%</span>
</div>
</div>
<div id="divNameMatch" class="divNameMatch flex-row_left divEnqInfo">
<div class="pad1x NameMatchiv">
<span class="labelValue" name="spnNameMatch" id="spnNameMatch2">100%</span>
</div>
</div>
<div id="divNameMatch" class="divNameMatch flex-row_left divEnqInfo">
<div class="pad1x NameMatchiv">
<span class="labelValue" name="spnNameMatch" id="spnNameMatch3">65.23%</span>
</div>
</div>
</div>