Choosing a symmetry
Symmetry is the number of identical wedges arranged around the centre. Six and eight fold designs read as flowers and leave large open areas, which is what young children need: a shape has to be big enough to fill without going outside the line.
Twelve and sixteen fold designs pack far more, smaller shapes into the same page. They take much longer to colour and reward fine-tipped pens over crayons.
Rings and how long a page takes
Each ring is a band of repeated petals between two circles. Three rings on a six fold design gives roughly eighteen shapes: a sitting the length of a picture book. Seven rings at sixteen fold gives over a hundred, which is an evening.
The centre is deliberately left as a small rosette rather than letting every petal converge on a point. Petals that all meet in the middle print as a solid blot of ink.
Printing so it actually fits
Print sets the page to US Letter or A4 with a half inch margin on every side and scales the design to fit inside it. Choose Fit to page in your printer dialog and turn off any additional scaling, or the outer ring will be trimmed.
Downloading the SVG gives you the vector file itself. It stays sharp at any size, so it can be enlarged to poster size or dropped into a design tool without going soft.
Why the lines are closed
Every outline in these designs is a closed loop. That matters if the page is coloured digitally: a fill tool escapes through any gap in a line and floods the whole page. It matters on paper too, because a broken line reads as a mistake rather than a boundary.