Thats normal with every microscope using direct light source creating unwanted reflection and erase some writing, you can ignore and use it like that and when you need to see the writtings you tilt the board and note down, if you want to fix you can always use a gooseneck or some kind of directional light source, but this mean more things on bench and more obstacles.
If you are using the microscope from that post, a good match will be something that attach to the tube, like:
https://www.ebay.co.uk/itm/183040658759As a bonus you can use both direct light and gooseneck for best performance and shadow free, (Set gooseneck to max brigthness and ajust led ring to min, will give you a good and clean view with visible writtings)