JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" class="amount_available"/>
<div class="multiple_spec">
    <div class="some_class">
        <input type="text" name="quantity1"/>
        <input type="text" name="quantity2"/>
        <input type="text" name="quantity3"/>
    </div>
</div
<div class="multiple_price">
    <div class="random_class">
        <input type="text" name="quantity4"/>
        <input type="text" name="quantity5"/>
        <input type="text" name="quantity6"/>
    </div>
</div>

JavaScript

var $quantityInputs = $(".multiple_spec input[name*=quantity]");

$quantityInputs.on('keyup',function(e){
    
    var amount_available = +$('input.amount_available').val(),
        total_quantity = $quantityInputs.map(function(i, el){
            return +$(el).val() || 0;
        }).get().reduce(function(prev, curr){
            return prev + curr;
        }, 0);
    
    if(total_quantity > amount_available){
        console.log('total quantity exceeds available amount - do something');
        $(this).val(function(index,value){
            return value.substr(0,value.length-1);
        });
    }
        
});