Trying to resurrect my darkroom after 20 years in the attic. All going well but I cannot find my instructions for a Polysales CdSe Enlarger Meter. It has a circular dial marked 'Paper Speed' with numbers 1-12, and on/off switch, sensor and a green 'Balance' light and a separate diffuser. Would appreciate anyone helping me out - particular with setting the paper speed. Thank you.