Explanation:

Holds good as to Rs. 90,000 but void as to Rs. 10,000. 

According to Section 126. When gift may be suspended or revoked

As per the Illustrations of Section 126

A gives a lakh of rupees to B, reserving to himself, with B's assent, the right to take back at pleasure Rs. 10,000 out of the lakh. The gift holds goods as to Rs. 90,000, but is void as to Rs. 10,000, which continue to belong to A.