"*" is shorthand for "1*". It’s a ratio, so if you have two rows, one with "*" and one with "10*", the former gets 1/11th of the available and the latter gets 10/11th of the space.
In your example above, "10*" is unnecessary – "*" would make more sense because there is only one row using ratio-based sizing, so any ratio will equate to 100% of the available space.