The round strike can be either a single or a double.
For the single roundstrike we cut a slicing Mittelhauw from left to right at neck level, then loop around for a right to left cut at thigh level, again a Mittelhauw, this is all done in a single tempo and thus with a single step we've described a semi-circle with our sword.
The double round strike is a pair of round strikes in alternate directions describing an S curve. We begin cutting right to left then left to right, all in a single tempo with a short advance step of the front step and a gathering of the rear. The final part of the S is struck with a lunging step of the front leg much more strongly.