Income tax on post office nss87 withdrawal

Respected Sir/Madam,

My mother had NSS 87 account in post office that was closed in Dec-17. Form 15H was submitted then at the time of closure so now tax is deducted at source. There's no entry under Form26AS as well.

What I am not sure about is, Is entire withdrawal amount taxable or only the Interest component?

Also should this income be reflecting under Income From Other Sources in IT Returns?

Thanks and kind regards.