adding combinations/variants for Google feed and perfect setup

[Pedalman]

Hello

I got a question concerning combinations or variants of a product.

 

Let's assume I got a new product in colors red and blue.
First I have to create a new product let's call it T-shirt
since it is a new product TB and PrestaShop asked me to enter name, the reference code of my shop for articles and EAN -13 number.

My shop sales already 99 products so the new product will be number 100 in the internal database. So I enter reference code 100.
Here comes the question

EAN -13 is specific for the variant blue or red. So I can skip it here and I have to enter these numbers under the tab of combinations.

Is this this the correct way or do I have to proceed in another way like:
the new product is also the first variant and I only add for example the red one.

 

My exported and shortened Google feed via module GoogleFlux:

<item>

<g:id>100-97</g:id>

<title><![CDATA[t-shirt]]></title>

<description><![CDATA[ "desc]]></description>

<g:gtin>1234</g:gtin>

<g:brand><![CDATA[brand]]></g:brand>

<g:mpn><![CDATA[9997]]></g:mpn>

<g:age_group><![CDATA[kids]]></g:age_group>

<g:item_group_id>100</g:item_group_id>

<g:color><![CDATA[blau]]></g:color>

<g:shipping>

    <g:country>DE</g:country>

    <g:service>Standard</g:service>

    <g:price>2.9 EUR</g:price>

</g:shipping>

<g:shipping_weight>0.10 kg</g:shipping_weight>

</item>

 

<item>

<g:id>100-98</g:id>

<title><![CDATA[t-shirt]]></title>

<description><![CDATA[desc]]></description>

<g:gtin>0739303852701</g:gtin>

<g:brand><![CDATA[brand]]></g:brand>

<g:mpn><![CDATA[9998]]></g:mpn>

<g:age_group><![CDATA[kids]]></g:age_group>

<g:item_group_id>100</g:item_group_id>

<g:color><![CDATA[rot]]></g:color>

<g:shipping>

    <g:country>DE</g:country>

    <g:service>Standard</g:service>

    <g:price>2.9 EUR</g:price>

</g:shipping>

<g:shipping_weight>0.10 kg</g:shipping_weight>

</item>