Context: Baljit takes some orders from Tim and Rita.
टिम - हमको पापड़ चाहिए।
बलजीत - आपको कितने प्लेट पापड़ चाहिए?
टिम - हमको एक प्लेट चाहिए। क्या नान है?
बलजीत - हाँ जी, ज़रूर, आपको कितनी नान चाहिए?
टिम - हमको दो नान चाहिए और एक बोतल मिनरल वाटर भी चाहिए।
बलजीत - कितना पानी, एक लीटर?
Tim - We want papadams.
Baljeet - How many plates do you want?
Tim - We want one plate. Are there naans?
Baljeet - Yes sir, certainly. How many naans do you want?
Tim - We want two naans and a bottle of mineral water as well.
Baljeet - How much water, one litre?
कितना means how many/how much. It behaves like the word काला black and agrees with the number and gender of whatever it is describing.
In Hindi many questions are asked with कितना are asked with ‘how’ in English.
The possessive postposition का is like English ‘s. It behaves like काला. It is written connected to pronouns but otherwise as an independent word.
Note the way that the agreement is with the thing, or person, that is possessed and not with the possessor as it is in English.