Eggs, fish, dairy and grains can contribute selenium. The amount in plant foods can vary with the soil they grew in, which is one reason a list from another country may give a different figure.
Begin with the food you actually eat
Write down your usual grains and whichever of eggs, fish or dairy you eat. Use a food table that specifies the food and weight. Leave room for variation if it gives a figure for a plant food from a different region.
If you are comparing two packs
Check whether both list selenium and whether the amount is per tablet or serving. Bring both labels to your pharmacist if you are deciding whether to take them together. Make a short food record · NIH selenium fact sheet
Can you take two wellness products together? Make an overlap list first
Read the source beside the number
Check whether a food table names the grain and where the sample came from. A precise number for a food grown elsewhere can still be a rough guide for the food in your kitchen. When comparing a list that includes eggs, fish or dairy, use only the foods you normally eat. If your source gives a figure for raw grain, label it as raw in your notes before comparing it with a cooked serving.