Take the reading for a whole minute with the pulse oximeter before jumping to conclusions.
The pulse oximeter mathematically extrapolates the pulse reading. For example it will measure the pulse in 15 seconds and multiply it by 4 to get a per minute reading. Which leaves a lot of scope for error.
The normal pulse reading is 60 to 100 beats per minute and the normal saturation is more than 95%
Health Tips
Make sure you don't have nailpaint on your finger.
Make sure that your hands are at normal temperature, warm them a little if you feel they're cold.
Rest and make your body relaxed before putting on the pulse oximeter.
Place the pulse oximeter on your index or middle finger, as they have the highest blood supply. Make sure that the screen faces you while taking a reading. Any hand can be used.
Place your hand on your chest near your heart and try reducing hand movement
Keep the pulse oximeter on your finger for at least a minute, till the reading stabilises.
Record the highest reading that flashes on the oximeter after it has established after 10 seconds.