edited to answer my own question:

It looks like it’ll be linear, ramping at 0.000625 ZEC/block for 35 days or 0.0005 ZEC/block for 43 days, stopping at 12.5 ZEC/block. For example, 0.0005 ZEC/block 1st block, 0.001 ZEC/block 2nd block, etc. It will be 2.5 minutes/block, 24 blocks/hour, 576 blocks/day. About 0.3 ZEC/block at end of 1st day, 0.6 ZEC/block on 2nd day, etc. Ends at 300 ZEC/hour.

Here’s the thread

(mining slow start · Issue #762 · zcash/zcash · GitHub)

Daira:

For concreteness, assuming a 10-minute target block time, suppose we set

the slope of the ramp to be 0.01 ZEC per block. That would take 5000 *

10 minutes = 34.7 days to reach 50 ZEC. The monetary base at that point

would be 0.01*(5000*5001/2) = 125025 ZEC (as compared to 250000 ZEC if there were no slow start).

nathan-at-least: (April 11, 2016)

the halving interval remains unaltered (assuming block size/target rate

remain unchanged), so even with the slow start ramp up, the halving

interval will still remain 210,000 blocks (assuming no change to block

rate/reward). Let’s henceforth call this proposal “Slow Start Alpha”.

zookozcash:

Great work, Jack! I choose linear 5000-block ramp. Thanks everyone for

your contributions. Remember about the “5000-block” part, though, that

we’re planning to reduce the block interval from 10 minutes to 2.5

minutes (#764). I guess that means we should multiply by 4 all the block-count constants above?

Diara:

In that case the block reward would increase by 0.000625 ZEC per 2.5

minutes. That would take 20000 * 2.5 minutes ~= 34.7 days to reach the

maximum of 12.5 ZEC/block. The block reward of 6.25 ZEC is skipped.

Another possibility that has slightly rounder numbers for the

2.5-minute block case, is a ramp of 0.0005 ZEC per block. This takes

25000 blocks to reach the full 12.5 ZEC reward, which takes 43.4 days.