Is Tour ranking 100% inspired to ATP ranking?

[inseedious]

I'm asking you this because the ATP ranking has, in addition to the well known "Top 18 results", the following features:

"The best 18 tournament results must include (even if it is NOT one of their best tournament results): all four Grand Slam results and eight of the nine ATP Tour Masters 1000 results (not including Monte Carlo) unless the player plays all 9 Masters 1000 events then he can have his best eight count.
The Grand Slams and the 8 Masters 1000 results account for 12 tournaments. The remaining 6 results MUST come from the player’s best four ATP 500 events and his best two ATP 250 results."

I'd like to know it, because, since I have had good results in ATP 250, I should not play ATP 500 anymore, unless I'll have the level to surely reach at least SF or F, because I have 5 good results in ATP 250 (one W, four F), and a 1st round in ATP 500 would delete me 150 points.

[BrushedBigJJ]

I want to add a question.

If you withdraw from a slam or masters event and get 0 points, is that tournement counted towards one of your 18 tournements?

[VMoe86]

I think this question is not just related to TE, so I moved the topic to the ITST Section on this forum. Cannot give definite answers to the questions, since I don't know how the ranking is actually implemented.

For inseedious' question I think that any combination of six ITST 250 and ITST 500 tournaments is possible, like six tournament victories in ITST 250 and only first round losses in ITST 500 will result in those six ITST 250 victories being counted for the ranking.

For BrushedBigJJ's question: Again, just a guess. If you look at your Points Breakdown, there are Slams, ITST 1000, ITST 500 respectively ITST 250. Under ITST 500/250 only your six best results in such tournaments are counted, so if you don't participate in a Slam or ITST 1000, you cannot replace it with a smaller tournament.