AIBU To have 6 year old stop crying before I start timer for time out?

[dipdapispants]

When 6 year old misbehaves I put him in time out. Every time he will tantrum and cry. He knows how long he has to sit there for. I don't start the timer until he is completely silent and sitting still. If he makes a sound, widgets, gets up I start the timer again. Sometimes he can be sat there 2 or 3 times longer than the set time.

Am genuinely don't know if this is the right thing to do?

Shameful sets out well how you use ignoring when siblings fight or antagonise. You could also say firmly "don't hit/kick whatever " then remove other sib and do something fun with them. NO further attention or speaking to misbehaving sib.

I thought the point of the naughty step was to give time to calm down away from the friction rather than a timed penalty of silence. The timing is needed to allow enough time but I wouldn't start from the beginning if not calm at the end of 6 mins. I would say you need more time, I will come back when you have calmed down. I would check back at 3 mins. If I had to do this again on the third time I would accept he is not able to self control his anger in this situation and try a different approach.
There are no rules tho

If you are questioning it you know it's not quite right at the mo. Follow your instincts, if you know he knows he has misbehaved stand strong. If he is causing a fuss because he has been caught out doing something wrong and that is what is annoying him stand strong. However, if you know he may not quite realise or understand why he is being told to take time out as the situation has grey areas then it is time to explain (in a very simple way).