Benny, there is 247 bets in all covering 8 different horses for all possibilities, but not sure what you mean by 4 races does that mean 2 horse race? if so much more complicated, you can do it long hand though e.g.

Doubles race a horses = 2
Doubles race b horses = 2
Doubles race c horses = 2
Doubles race d horses = 2

so doulbles race a&b =2x2 = 4 bets, youve got this 6 times,( i.e. a&b, a&c, a&d, b&c,b&d, c&d) so you've got a total of 24 doubles.

same process for trebles i.e. 2x2x2= 8 betsx 4 times = 32 bets

to cover the accumalator its 2x2x2x2 16 bets,
So to cover the lot is 72 bets.

In my opinion it would be better to cover 2 horses in each bracket from different races rather than 2 horses from each race as you know youve got 4 losers and 61 losing bets b4 you start.