Set hflex to Column calculate a wrong width

<zk>
<grid width="300px">
<columns>
<column hflex="1">
<label value="A" />
</column>
<column hflex="1">
<label value="B" />
</column>
</columns>

<rows>
<row>
<label value="C" />
<label value="D" />
</row>
<row>
<label value="E" />
<label value="F" />
</row>
</rows>
</grid>
<grid width="300px">
<columns>
<column hflex="1" label="A" />
<column hflex="1" label="B" />
</columns>
<rows>
<row>
<label value="C" />
<label value="D" />
</row>
<row>
<label value="E" />
<label value="F" />
</row>
</rows>
</grid>
</zk>