So long as the contract specifies your hours and you are required to record this time, then you have to fulfil that and you record the actual time that you spent. The Prophet (peace and blessings of Allaah be upon him) said: “The Muslims are bound by their conditions.” Narrated by al-Tirmidhi (1352) and Abu Dawood (3594); classed as saheeh by al-Albaani in Saheeh al-Tirmidhi.
With regard to the excuses that you have mentioned, such as the driver needing money and your having done the work required in full in less time, and that other workers waste time in things that do not help the work, and that you are a mother with other responsibilities, all of that does not make it permissible to tell lies or betray the trust. You have been entrusted to work a certain number of hours and to record that.
You have two choices:
1 – You can tell the administration what is really going on, and that you are able to complete the work required of you in less than the time specified, then after that you can work on the basis of whatever you agree upon with them.
2 –Or you can write down the hours that you actually work – without adding anything – so that you will not take any money that you are not entitled to.
With regard to the salaries that you received before, you have to return them to the administration if possible. If that is not possible then you should deduct them from your future salaries.
We ask Allaah to help and guide us and you.
And Allaah knows best.