/* Добавьте position: relative к карточке */
.t-store__card {
    position: relative !important;
}

.t-store__card::after {
    content: attr(data-product-inv) " шт. в наличии";
    font-family: 'Gogh', sans-serif;
    font-size: 12px;
    color: #fefefe;
    background-color: rgba(0, 0, 0, 0.8);
    padding: 4px 8px;
    position: absolute;
    top: 10px;
    left: 10px;
    z-index: 999;
    width: auto;
}

.t-store__card__btns-wrapper {
    margin-top: 40px !important;
}

.js-store-prod-sold-out {
    display: none;
}

/* Для ::before тоже добавьте явные координаты */
.js-product::before {
    content: attr(data-product-inv) " шт. в наличии";
    font-family: 'Gogh', sans-serif;
    font-size: 14px;
    color: #000;
    background-color: #fefefe;
    padding: 3px 8px;
    position: absolute;
    top: 10px;
    left: 20px;
    z-index: 999;
}

.t-store__prod-popup__name {
    margin-top: 5px;
}

@media screen and (max-width: 1240px) {
    .js-product::before {
        left: 5px;
    }
}

@media screen and (max-width: 640px) {
    .js-product::before {
        position: relative;
        top: 0;
        left: 50%;
        transform: translateX(-50%);
    }
}