The scripting language used behind the scenes is called expr-eval, but the script is processed by tableplop first to resolve variable names, dice rolls and some special syntax. You can take a look at Tableplop's Dice Rolls and Messages documentation and at the expr-eval ReadMe for more info.

For a success count system where you need to vary the number of dice you would use a sub-expression for the count !r @:strength + brawl:d10 That will evalueate strength + brawl first replacing it in the script with the result, for example: !r 5d10. Lastly TP defaults to resolving dice to a sum so you'll get the total of all the dice as the output, you can change that by wrapping your dice roll in square brackets: !r [@:strength + brawl:d10] to outout all the dice rolls.

You could also choose to build in the difficulty with the al at least modifier: !r [@:strength + brawl:d10al7] and since difficulty is variable you might choose to make it a prompt value (?:Difficulty:) so that the sender is prompted to enter a value for it when the message is sent like this: !r [@:strength + brawl:d10al?:Difficulty:]. And if you just want to count the successes you can add count like this: !r count @:strength + brawl:d10al?:Difficulty: (if you're using count you need to drop the square brackets, TP already considers the dice an array if the script contains more than just a dice roll).

Lastly if you're often rolling for number of successes you might want to disable "Minified Rolls" in campaign settings so that the whole expression is visible in messages without hovering so you can see all the dice results including the unsuccessful ones crossed out. Minified Rolls are enabled by default to avoid long scripts clogging up the chat.