This is the 3729th most frequent Russian word.
учет
Accounting; record-keeping; registration.
In this sentence, 'учет' is being used to mean 'accounting' or 'tracking,' referring to keeping an organized record of expenses.
Он ведёт учёт своих расходов.
He keeps track of his expenses.
Here, 'учет' refers to the practice of monitoring or accounting for the number of visitors entering the museum.
Учёт посетителей в музее строго контролируется.
The accounting of visitors in the museum is strictly monitored.
In this example, 'учета' denotes tracking or accounting, specifically of worked hours for organizational purposes.