Such a low power is due to accommendation, the power of eye to change focusing. If you are spending lot of time on gadgets, phones chatting etc. If the prescription is given without, dilating and doing post mydriatic test, i do not recommend you to be careful.
Next Steps
get mydriatic refraction done and confirm power with post mydriatic test. this excludes accommodative prkblems
Health Tips
stop using smart phone and gadgets like notebooks, or minimize use.