Nah, I just failed at basic arithmetic :D

I wrote this:

  <div class="memory" bytes="32">
    <malloc size="4" addr="0x0"></malloc>
    <malloc size="5" addr="0x4"></malloc>
    <malloc size="6" addr="0x9"></malloc>
    <malloc size="7" addr="0xa"></malloc>
    <free addr="0x0"></free>
    <free addr="0x4"></free>
    <free addr="0x9"></free>
    <free addr="0xa"></free>
  </div>

Instead of this:

  <div class="memory" bytes="32">
    <malloc size="4" addr="0x0"></malloc>
    <malloc size="5" addr="0x4"></malloc>
    <malloc size="6" addr="0x9"></malloc>
    <malloc size="7" addr="0xf"></malloc>
    <free addr="0x0"></free>
    <free addr="0x4"></free>
    <free addr="0x9"></free>
    <free addr="0xf"></free>
  </div>