As many as you want. However, only 3 buy ads and 3 sell ads can be active at any time, and these ads cannot have identical descriptions, limits, and exchange rates.
For example,
If you already have an active ad with an exchange rate of 10%, you can't have another active ad with the same rate.
If you already have an active ad with a minimum order limit of 10 USD and a maximum order limit of 50 USD, you can't have another active ad with a minimum order limit of 40 USD and a maximum order limit of 100 USD because the range overlaps with the first ad.
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