Olivia took an umbrella while leaving the house.

In the given sentence, the word an points out an object and indicates its number.

Hence, the word an is limiting adjective.

This truck is made in Japan.

In the given sentence, the word This points out a particular thing.

Hence, the word This is a demonstrative adjective.

That is a dress made of silk fabric.

In the given sentence, the word a points out an object indicating its number, and the word that points to a particular thing.

Hence, the word a is limiting adjective and that is a demonstrative adjective.