Head soft spots

When should the baby's soft spot fuse? Because I read a lot on Internet and found that it's normal to fuse anywhere between 4 months to 18 months but my baby's doctor said it should be between 14 months to 18 months 🤔 my baby's development is all good but doctor told me in recent appointment that his soft spot is but small and my baby is four month old. Referred my baby to neurologist I am so worried I am talking about the upper spot not back one