Static compression ratio is the mathematical ratio between the entire volume of the cylinder and combustion chamber when the piston is at bottom dead center and the volume when the piston is at top dead center. The combustion chamber volume is part of both numbers.
Here's a simplified example:
Swept volume of cylinder = 50 cubic inches.
Volume of combustion chamber = 5.19 cubic inches (85cc).
Total volume of cylinder at BDC = 55.19 cubic inches.
Compression ratio = 55.19/5.19 = 10.6:1
Swept Volume = 50 cubic inches
Volume of combustion chamber = 5.86 cubic inches (96cc)
Total volume of cylinder at BDC = 55.86 cubic inches
Compression ratio = 55.86/5.86 = 9.53:1
Before anyone jumps in to tell me I'm not figuring in deck height, piston dome volume, gasket thickness etc., etc., this was not intended to be a full tutorial on compression ratios. All those numbers are assumed to be the same for both examples.
Jerry