Practise copying from ready-made word lists or upload your own.
If you are using "Shuffle" to randomise the order then you might want to use "Once each" as well to ensure each word gets chosen just once.
Choosing "Repeat" is the same as manually pressing the "Next" button after every play.
If playing through in order (no shuffle), it will match the number of plays of the previous word. To play each word twice in order, click on the first word then press "Repeat" and "Play".
If you change mode after playing just some words it will do its best to follow the new mode but you might need to press "Reset" to get what you need.
If you use the speech function then the pause between words might be longer than you specify: it makes sure that the speech finishes before moving on.
This trainer is known to work well in the latest Chrome, Firefox, Safari and Edge web browsers, including mobile versions (which implement the Web Audio API and can be downloaded here). It works, with some sound artefacts, in recent versions of Internet Explorer (where it has to use Flash).
I'm already aware of and working on these issues: