PWM wave start

I need to generate a square wave with a period of 5us, duty cycle 50%, a dead time between H and L outputs of 0.5 us. I configured the PWM channel 0 as follows:

// No prescaler, devider A =21
REG_PWM_CLK = 0x00000015;

REG_PWM_CMR0 =
    0b1011 //Clock A (PREA, DIVA)
    | 0x00000100 //center aligned
    | 0x00010000; //dead time enabled
//Since counter clock is 4MHz, CPRD must be 10 (center-aligned implies period=2.5us instead of 5us)
REG_PWM_CPRD0 = 10;
//>> Duty cycle
REG_PWM_CDTY0 = 5;
//>> Deadtime=0.5us 
REG_PWM_DT0 = 0x00020002;

I start PWM channel 0 with

REG_PWM_ENA = 0x1;

The waveform is what I was looking for, except for the start: the very first square is smaller then the other and that’s always so (please see attachment).
Any idea why this happens? Some register may correct that issue?
Thank you in advance

It looks like it might be half of the intended waveform. That would indicate that by using the center-aligned mode, starting the counter at zero will be halfway through one of the peaks.

Pre-load the timer with a different value.

Thank you MorganS for your reply. I don't think it is possible to Pre-load the counter value of the PWM: as stated by the ATMEL datasheet, the PWM Channel Counter Register (PWM_CCNTx) is read-only (please refer to page 1050 of SAM3X datasheet). On the same page you'll find also that the register value is reset to 0 whenever you enable the channel.