foundry/Data/modules/levels/templates/tooltip.html

<form id="{{id}}" class="{{classes}}" data-appid="{{appId}}" autocomplete="off">
    <span class='name'><i class="fas fa-arrow-up"></i></span>
    <span class='value'>{{#if_null flags.levels.rangeTop}}
        <i class="fas fa-infinity"></i>
    {{else}}
        {{{flags.levels.rangeTop}}}
    {{/if_null}}
    </span>
    <span class='name'><i class="fas fa-arrow-down"></i></span>
    <span class='value'>{{#if_null flags.levels.rangeBottom}}
        <i class="fas fa-infinity"></i>
    {{else}}
        {{{flags.levels.rangeBottom}}}
    {{/if_null}}
    </span>
</form>