Visit visa for my mother refused from Pakistan

[Scorpio758]

Hi All, I am a british citizen and my mother’s visit visa recently refused from Pakistan. She applied fir 3 weeks visit. Her entire trip is sponsored by her husband in Pakistan whilst food and accommodation by myself in UK. She is a house wife and financially dependent on my father since married. I also attached property/land documents on my fathers name generating regular income every month. I also mentioned my mother receives 20,000 PKR every month from her son(attached a confirmation letter from her son and his payslips) in Pakistan which is for personal use/expenses only. Theres a question in application form how much money are you personally planing to spend on trip. I put £1000. Then theres an other subsequent question asking who else will be paying for your trip. I mentioned my fathers details and £1000. Now refusal letter says you stated that you will be spend £1000 on your trip which leads your discretionary income to nill. The reality is entire trip cost is £1000. I might have got this wrong. ECO might have thought that £1000 from husband and £1000 personal equals to £2000 but the fact is entire trip cost is £1000 which will be sponsored by husband.
I am planning to reapply her visa. Should I mention in a cover letter that entire trip cost is £1000? What shall I mention in the question where they ask how much money are you personally planning to spend? Thanks