The gigs required to complete any task must be requested at the time of order in order to preserve a professional practice
Had you previously discussed your project or the required amount of gigs with the buyer? It could be that the buyer didn’t fully look over your order until they started working on it, which could be some time after you’ve ordered.
For example, my gig offers editing and proofreading services at a rate of $5 per 2,000 words. Sometimes, I get a $5 order from a buyer and am not able to actually begin working on the order until several days after they’ve ordered due to my workload. I begin my work, open their document and see that it contains way more than 2,000 words! Well, I then have to contact them to inform them that for their $5 order, I will either only be able to edit the first 2,000 words or they will need to purchase additional gigs to cover the size of their project. Because I was not able to start working on their project and fully understand its size until several days after they ordered, they would not receive this notification until then.
In that case, I feel that it’s the buyer’s responsibility to read a seller’s gig description, understand their rates and order accordingly. Because there wasn’t much information provided in your original post, though, I’m not sure if your case is similar. Your issue could be entirely different.
Either way, if there’s any question or doubt about how much a project will cost or how many gigs may be required, it’s always a great idea to contact the seller prior to ordering. That way, you can clarify the expected fee and avoid any surprises after placing your order.