Digital oscilloscope maximum input voltage
The maximum voltage is &plusmn;300V, period.

It doesn't matter what the settings on the scope are, or whether the voltage is AC or DC.

Any voltage less than that will not damage the scope, but what you see on the display may or may not be useful, depending on the settings.

You can use a 10&times; probe to measure higher voltages &mdash; up to whatever the probe is rated for &mdash; but if you ever switch the probe to 1&times; while doing so, you'll be violating the scope specification.