There's lots of variables to consider, track condition, how many trials have gone before you, dogs fitness, solo or group and so on so comparing your trial with other trials on the day and run home times on the day is the best bet but as a guide only......if a maiden dog was trialling 23.30 or so it would be a good time, low 23's a very good time and up around 23.60 or so would probably be needing an excuse. Maidens tend to get won in around 23.1-23.4 most weeks.