So you need a INPUT text area, instead of dropdown, am I right?
Then try this:
Open the same PHP file:
eca-trade.com/templates/gk_yourshop/html/com_virtuemart/productdetails/default.php
find this Lines:
<div class="FlexibleProductDetailsSelectBox">
<select name="quantity[]" class="quantity-input js-recalculate">
<option value="61">61</option>
<option value="41">41</option>
<option value="31">31</option>
<option value="21">21</option>
<option value="11">11</option>
<option value="10">10</option>
<option value="9">9</option>
<option value="8">8</option>
<option value="5">5</option>
<option value="4">4</option>
<option value="3">3</option>
<option value="2">2</option>
<option value="1">1</option>
</select>
</div>
and replace it with this:
<span class="quantity-box">
<input type="text" class="quantity-input js-recalculate" name="quantity[]" value="61"/>
</span>
<span class="quantity-controls js-recalculate">
<input type="button" class="quantity-controls quantity-plus"/>
<input type="button" class="quantity-controls quantity-minus"/>
</span>
The result will be like this:
Attachment ScreenShot2013-01-23at12.33.27PM.png not found
The default value is 61 and visitors are able to increase/decrease the quantity to what ever they like.
Regards.