Shrink size of map

Hi,

I’ve managed to insert the block but it takes up full page width. As you can see from screenshot below, my blog uses 780 width.
I tried adjusting to custom size and changing width to 780, but then the block moved to be left aligned.

at 100%: https://imgur.com/a/rmr95jl

adjusted to 780: https://imgur.com/K76mPKB

initial code is

<ins class="bookingaff" data-aid="2381901" data-target_aid="2381901" data-prod="map" data-width="100%" data-height="590" data-lang="ualng" data-dest_id="0" data-dest_type="landmark" data-latitude="41.3873974" data-longitude="2.168568" data-landmark_name="Barcelona" data-mwhsb="0" data-address="Barcelona, Spain">
    <!-- Anything inside will go away once widget is loaded. -->
        <a >Booking.com</a>
</ins>
<script type="text/javascript">
    (function(d, sc, u) {
      var s = d.createElement(sc), p = d.getElementsByTagName(sc)[0];
      s.type = 'text/javascript';
      s.async = true;
      s.src = u + '?v=' + (+new Date());
      p.parentNode.insertBefore(s,p);
      })(document, 'script', '//cf.bstatic.com/static/affiliate_base/js/flexiproduct.js');
</script>

When i tried to adjust code to centre, it failed and would no longer show the map

<div style="display: flex; justify-content: center;">
    <ins class="bookingaff" data-aid="2381901" data-target_aid="2381901" data-prod="map" data-width="780" data-height="300" data-lang="ualng" data-dest_id="0" data-dest_type="landmark" data-latitude="41.3873974" data-longitude="2.168568" data-landmark_name="Barcelona" data-mwhsb="0" data-address="Barcelona, Spain">
        <!-- Anything inside will go away once the widget is loaded. -->
        <a >Booking.com</a>
    </ins>
</div>
<script type="text/javascript">
    (function(d, sc, u) {
      var s = d.createElement(sc), p = d.getElementsByTagName(sc)[0];
      s.type = 'text/javascript';
      s.async = true;
      s.src = u + '?v=' + (+new Date());
      p.parentNode.insertBefore(s, p);
      })(document, 'script', '//cf.bstatic.com/static/affiliate_base/js/flexiproduct.js');
</script>

can you please advise

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