.cluster_custom {
    font-size: 13px;
    line-height: 1;
}
.cluster_custom > span {
    position: absolute;
    left: 0;
    right: 0;
    text-align: center;
    z-index: 1;
    line-height: 56px;
}
.ymaps-balloon-info {
    font-size: 14px;
}