Can I keep score of a Fast4 match on Apple Watch?

Yes. In Tennis Time, choose Fast4 under Set type on the Match tab. Sets go to 4 games with No-Ad scoring, a tiebreak to 5 at 3-3 and a deciding point at 4-4. Fast4 is part of Pro.

What is a match tiebreak?

A tiebreak to 10 points, won by two, played instead of a full deciding set. In Tennis Time choose Match-TB under Deciding set, or Match TB under Sets for a match that is only the tiebreak.

What does No-Ad scoring mean?

At deuce the next point wins the game, instead of needing two points in a row. The receiving side chooses which court to receive from.

Match formats: sets, tiebreaks, Fast4, pro sets and No-Ad

Tennis Time keeps score in the formats players actually use: best of 1, 3 or 5 sets, a match tiebreak to 10, Fast4, an 8-game pro set and short sets, with Advantage or No-Ad scoring. Choose them on the Match tab before you start.

Choose the format

On the Ready screen, swipe to the Match tab.
Tap an option in each section: Sets, Deciding set, Set type, Scoring and Games per set.
Tap the small i next to a section's name to read how each option works.

Ready screen, Match tab, with Presets, Save as preset and the Sets options — The Match tab.

The format you start a match with becomes the default for the next one. To set the default without starting a match, go to Settings > Format.

Sets

Best of 1: A single set decides the match.
Best of 3: The first side to win two sets. This is the default.
Best of 5: The first side to win three sets.
Match TB: No sets at all: one tiebreak to 10 points, won by two, decides the match.

Deciding set

For best of 3 and best of 5, choose how the last set is played.

Tiebreak: The deciding set is played like the others, with a tiebreak at games-all.
Match-TB: Instead of a deciding set, one tiebreak to 10 points, won by two, decides the match.
Advantage: No tiebreak in the deciding set. It goes on until a side leads by two games.

Set type

Standard: A set goes to the number of games you pick, won by two games. At games-all a tiebreak to 7 decides it.
Fast4: A short set to 4 games with No-Ad scoring. At 3-3 a tiebreak to 5 decides it, with a deciding point at 4-4. Pro.
Pro set: A single set to 8 games, with a tiebreak at 8-8. Choosing it sets the match to one set. Pro.
Short set: The first side to reach the number of games takes the set. No tiebreak, no margin of two.

Scoring

Advantage: At deuce (40-40) a side must win two points in a row: the first gives advantage, the second the game.
No-Ad: At deuce the next point wins the game, and the receiver chooses which side to receive from.

Games per set

Choose 3 Games, 6 Games or 9 Games. 6 is the classic set. With Custom (Pro) you pick any number from 1 to 12 with the arrows.

Change the format during a match

Tap the gear, then Match. After the first point, rules that would change the games already played are marked Would change the games already played, so the score never rewrites itself.

Free and Pro

Standard and short sets, 3, 6 or 9 games, Advantage and No-Ad, best of 1, 3 or 5, the match tiebreak and every deciding-set rule are free. Fast4, the pro set, custom games and presets are part of Pro.

Questions

Can I keep score of a Fast4 match on Apple Watch?: Yes. In Tennis Time, choose Fast4 under Set type on the Match tab. Sets go to 4 games with No-Ad scoring, a tiebreak to 5 at 3-3 and a deciding point at 4-4. Fast4 is part of Pro.
What is a match tiebreak?: A tiebreak to 10 points, won by two, played instead of a full deciding set. In Tennis Time choose Match-TB under Deciding set, or Match TB under Sets for a match that is only the tiebreak.
What does No-Ad scoring mean?: At deuce the next point wins the game, instead of needing two points in a row. The receiving side chooses which court to receive from.