xdt file: Does the ElementType ID="??" sequence matter?

Dear All

Regarding the xdt file. Does the ElementType ID="??" sequence matter?
Does

<ElementType ID="21" content="eltOnly" history="F" name="descripGrp" order="many">

need to have a lower ID, than

<ElementType ID="22" content="mixed" name="descrip" order="many" type="string">

because descrip is a child of descripGrp?

Regards,
Marco