Grammar

2.236 numbers with ordinals and postdeterminers

You can use cardinal numbers with both ordinals (see paragraphs 2.249 to 2.256) and postdeterminers (see paragraph 2.44). When you use a cardinal number with a determiner followed by an ordinal number or a postdeterminer, the cardinal number usually comes after the determiner and the ordinal or postdeterminer.

The first two years have been very successful.
...throughout the first four months of this year.
...the last two volumes of the encyclopedia.
...in the previous three years of his reign.

Note that some postdeterminers can be used like ordinary classifying adjectives (see paragraph 2.44). When they are used like this, the cardinal number comes before them.

He has written two previous novels.
...two further examples.