Why does Gulliver stay at St. George for three weeks ? Why does the captain remain at Tonquin and send Gulliver along with 14 seamen in sloop ?

From the text:

We set out the 5th day of August, 1706, and arrived at Fort St. George the 11th of April, 1707. We staid there three weeks to refresh our crew, many of whom were sick.

From thence we went to Tonquin, where the captain resolved to continue some time, because many of the goods he intended to buy were not ready, nor could he expect to be dispatched in several months. Therefore, in hopes to defray some of the charges he must be at, he bought a sloop, loaded it with several sorts of goods, wherewith the Tonquinese usually trade to the neighbouring islands, and putting fourteen men on board, whereof three were of the country, he appointed me master of the sloop, and gave me power to traffic, while he transacted his affairs at Tonquin.