I just looked at it. It’s normal behaviour.
You registered your orders as limit orders.
There are 2 types of transaction order : limit and market (take a look at the combobox at the top of the buy action window)
When you buy at market your order will be executed at any price on the market. For instance if you try to buy 50’000 shares of ACME at market, the system will execute your order at the best price (note that you can’t set a transaction price). For instance it could sell 10’000 shares at $52.98 and 40’000 shares at $49.87. You are guaranteed to have your order executed (if there are enough shares on the market).
If you buy at limit the system won’t exceed the price limit you set. Only the matching sell transactions with prices under your limit price will be executed. This may results in a partial execution of your buy order.