How is ARR of TIM1 relevant if TIM1 is triggered by TIM2

[MagnusNTNU]

Hi, I am using a STM32F411CEU6. I am trying to make the One Pulse Mode of TIM1 start every time TIM2 has counted its ARR. 

However, I don't seem to really understand what the relevancy of the ARR of TIM1 is when having  TIM2 controlling the start(except if it is longer than TIM2 ARR i guess). Now I have 90MHz on both APB1 and APB2 and the PSC of both TIM1 and TIM2 is 90. I was following an example online where he sat the ARR of TIM1 to 50000 and ARR of TIM2 to 60000. The Pulse of TIM1 was 10000. From my understanding when I am running in output compare mode PWM1, TIM1 should start every 60ms and have a ON time of 10ms. 

Instead I see an ON time of 20ms and a period of 60ms. However when I change the ARR of TIM1 this ON time also changes. 

Is there something I am missing completely here? (I also have to change the OCMODE of TIM1 to PWM1 because it does not seem to be an option in MX)

Thanks in advance!

[MagnusNTNU · Accepted solution]

I didn't know that the TIM1 signal went high again after the ARR of TIM1. I figured it out now.