Even and Odd Selector filters are not working properly

Even and Odd Selector filters are not working properly

Hi, Hope you are doing fine. We are using Jquery version 3.3.1.Below is the explanation about the bug.
This our javascript Code
$(function(){
$("p.myp1 span:even").html("this is text using Class Name")
});
This is our Html Code.

<p class="myp1">
<span>My 1 Span</span>
<span>My 2 Span</span>
<span>My 3 Span</span>
<span>My 4 Span</span>
<span>My 5 Span</span>

</p>

While I tried to select even elements then its selecting odd elements . And same as while i tried to select odd elements then its selecting even elements . Please explain this or report it as bug in Jquery-3.3.1.

Thanks for your valuable time.