What will happen to an uninterruptible power supply if you connect a load to it twice as high as its rated power?

Question

Iron

There is a 250W uninterrupted power supply, you can say for free, and there is a computer, in which the PSU costs 700W, but in fact it should consume no more than 200 (this is the sum of the capacities of all its individual components). In this connection, the question is, what will happen if this computer is connected to this uninterruptible device? Long-term work in the event of a power outage is not required, only "hold on" for 10-15 seconds, that's how much energy periodically disappears in my area (usually during a thunderstorm).