Learn Russian: Как только часы покажут десять минут второго, мы начнём расчёт. - As soon as the clock shows ten minutes past one, we will begin the calculation.

In Russian, to tell time in the first half of the hour, you state the minutes that have passed and then use the Genitive ordinal number for the upcoming hour. Here, 1:10 is expressed as ten minutes into the second hour (второго). So, literally, it means "ten minutes of the second".

Why is the verb покажут in the future tense if the English translation says "shows"?

In English, we use the present tense after time conjunctions like "as soon as" (как только) or "when" (когда) even for future events. Russian is more literal: if the action happens in the future, you must use the future tense. Since both showing the time and beginning the calculation happen in the future, both покажут and начнём are in the future tense.

Why is the plural verb покажут used for a single clock?

The Russian word for clock or watch, часы, only exists in the plural form (just like "scissors" or "pants" in English). Because the noun is plural, any verb agreeing with it must also take the plural form.

What is the infinitive of начнём, and why use the perfective aspect here?

The infinitive is начать (to begin). It is perfective because it refers to a single, concrete future action (starting the calculation) that will happen immediately after the first condition is met.