I know the landlord has 15 days to return the security deposit or the landlord has 30 days to give the tenant written notice by certified mail to the tenant's last known mailing address if there are deductions due to damage, etc.

My question is does this mean the landlord must ensure the renter that they will have the check in hand within 15 days or does it mean the mailing date must be within the 15 days?

"83.49 Deposit money or advance rent; duty of landlord and tenant.—
...
(3)(a) Upon the vacating of the premises for termination of the lease, if the landlord does not intend to impose a claim on the security deposit, the landlord shall have 15 days to return the security deposit together with interest if otherwise required, or the landlord shall have 30 days to give the tenant written notice by certified mail to the tenant’s last known mailing address of his or her intention to impose a claim on the deposit and the reason for imposing the claim. The notice shall contain a statement in substantially the following form:
...
If the landlord fails to give the required notice within the 30-day period, he or she forfeits the right to impose a claim upon the security deposit."

The statute doesn't say how the LL is to return the deposit within 15 days. It doesn't say "mailed", so the LL could send it any way he/she chooses. Therefore I would say that it is up to the LL to make sure it actually gets to the tenant within that 15 days.

On the other hand, if LL is going to give the 30-day notice, it does specify the method of delivery. Since it says "... give the tenant written notice by certified mail ...", it appears that the LL's duty is fulfilled upon mailing.

So I didn't get my deposit within 15 days. I called and they said the check was cut on April 18th and that I should receive it by the 22nd. So they didn't hold to their own lease. Big deal, what penalties do they face by not sending it in time? If there are no consequences, there is no reason for the law.

What if at the walk through that the landlord didn't say there was any damamge... he also states that he will mail the secuirty ck out.. then about a week later when you ask him if he sent it out and he states that there is damage and in a few weeks after he gets back from vacation, he will let me know what the damage it and how much it will cost (he doubts it will go over what he has as security).
Can he be held accountable for the fact that he didn't say anything at the last walk through?