On the website, the game Quake II (ID: 286) has 20 similar games, but the API only returns 10.

https://www.igdb.com/games/quake-ii

fields name, similar_games.name; where id = 286;

[
{
"id": 286,
"name": "Quake II",
"similar_games": [
{
"id": 7351,
"name": "Doom"
},
{
"id": 356,
"name": "Quake 4"
},
{
"id": 333,
"name": "Quake"
},
{
"id": 312,
"name": "Doom II: **** on Earth"
},
{
"id": 231,
"name": "Half-Life"
},
{
"id": 355,
"name": "Quake III Arena"
},
{
"id": 2031,
"name": "Wolfenstein: The New Order"
},
{
"id": 281,
"name": "Return to Castle Wolfenstein"
},
{
"id": 1006,
"name": "Syndicate"
},
{
"id": 342,
"name": "Duke Nukem 3D"
}
]
}
]