You are reading the documentation for SDK v2, which is no longer the latest version. Switch to current
ChangeCartLineItemQuantity
export type ChangeCartLineItemQuantity = {
lineItemId: Scalars['String'];
quantity: Scalars['Long'];
externalPrice?: InputMaybe<BaseMoneyInput>;
externalTotalPrice?: InputMaybe<ExternalLineItemTotalPriceDraft>;
};