Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
How many values of r z (arcsecond) correspond with a r y (arcsecond) value of −0.247?

### Inputs:
table_name: table, columns: ['Region', 'Start datum', 'Target datum', 'c_x ( Metre )', 'c_y (Metre)', 'c_z (Metre)', 's ( ppm )', 'r x ( Arcsecond )', 'r y ( Arcsecond )', 'r z ( Arcsecond )']

### Response:
SELECT r z ( Arcsecond ) FROM table WHERE r y ( Arcsecond ) = −0.247