XtraMath is designed to measure what basic math facts students can recall, not what they can calculate. Before starting XtraMath, students should already be able to solve the problems without time pressure.
By default, students are assigned a six-second program, which gives them the most time to answer. This means correct answers entered within six seconds are considered fluent, and the student has twenty seconds before timeout (when the correct answer is shown).
The six-second threshold is the longest threshold currently available. If students are currently assigned a custom three-second program, you could switch them to the six-second program, giving them more time to answer.