pureininzuu wo kakuninsuru.

It is read:

プレイにんずう を かくにんする

Breakdown:

• プレイ = play
• 人数（にんずう） = number of people
• 確認する（かくにんする） = to confirm, check

So the whole phrase is プレイにんずうをかくにんする.

人数 means the number of people.

It is made of:

• 人（にん） = person / people
• 数（ずう） = number

So プレイ人数 literally means something like the number of people for play, which in natural English becomes number of players.

Japanese often makes compact compound nouns, especially in game menus, apps, labels, and product descriptions.

So:

• プレイ人数 = number of players / supported number of players

Even though プレイヤー means player, Japanese often prefers shorter label-style expressions like プレイ人数 in UI or packaging.

A native English speaker might expect something more literal, but Japanese frequently uses concise noun compounds like this.

を marks the direct object of the verb.

Here:

• プレイ人数 = the thing being checked
• 確認する = to check / confirm

So プレイ人数を確認する means to check the number of players.

You can think of を as showing what the action is done to.

The dictionary form is very common in Japanese for:

• headings
• menu text
• instructions
• button actions
• neutral descriptions of actions

So 確認する here does not necessarily sound like a plain statement such as I check. In context, it may feel more like:

• Check the number of players
• To check the number of players
• Check player count

Japanese often uses the plain dictionary form in interfaces and labels where English might use an imperative or a short noun phrase.

Not exactly.

• 見る means to look at / see
• 確認する means to confirm / check / make sure

So 確認する suggests more than just looking. It implies checking something carefully or verifying it.

For example:

• プレイ人数を見る = look at the player count
• プレイ人数を確認する = check/confirm the player count

In many situations, 確認する sounds a little more purposeful.

No subject is stated, and that is very normal in Japanese.

Depending on context, it could mean:

• you check the number of players
• the user checks the number of players
• one checks the number of players

In Japanese, subjects are often omitted when they are obvious from context. In a menu or instruction, the understood subject is often the user.

In normal Japanese writing, there would usually be no spaces:

プレイ人数を確認する。

Spaces are often added in learning materials to make the parts easier to see. They are not normally written that way in native text.

Grammatically, yes, it can be a complete sentence, but in many real contexts it works more like a label or instruction.

Depending on where you see it, it could function as:

• a plain statement: (Someone) checks the number of players
• an instruction: Check the number of players
• a menu item: Check player count

Japanese often uses sentence-like forms very flexibly in UI text and short instructions.

Yes. 確認する can mean both confirm and check, depending on context.

Common English translations include:

• check the number of players
• confirm the number of players
• verify the number of players

In a game or app interface, check is often the most natural English choice, but confirm is also possible if the context is about making sure the information is correct.