The damage die of your Hunter's Mark is a d10 rather than a d6.
Foe Slayer
Raw data
{
"name": "Foe Slayer",
"page": 121,
"level": 20,
"srd52": true,
"__prop": "classFeature",
"source": "XPHB",
"entries": [
"The damage die of your Hunter's Mark is a {@damage d10} rather than a {@damage d6}."
],
"className": "Ranger",
"classSource": "XPHB",
"basicRules2024": true
}