Update: You can close this topic. I solved it by creating a unique class per image and added to css code like so:

.av-image-hotspot_inner::after {
content: ”;
color: white;
left: -3px;
position: relative;
}

div .plattegrond1 .av-image-hotspot:nth-child(1) .av-image-hotspot_inner::after {
content: ’21A’;
}

div .plattegrond1 .av-image-hotspot:nth-child(2) .av-image-hotspot_inner::after {
content: ’21B’;
}

.av-image-hotspot_inner {
color: transparent !important;
}